When reading into World War 2 naval battles such as the Battle of the Coral Sea, The Battle of Midway, The Battle of Salvo Island, etc, it is shocking how frequently an excerpt like the following appears:
Despite taking overwhelming damage, the crew miraculously kept the vessel afloat for days until she was scuttled the morning of ____ by the vessel ____
Why did so many vessels get scuttled in World War 2? It seems like an immense waste of resources -- an overly-safe defensive measure that burns millions of taxpayer funds.
Are the logistics behind the recovery of a seriously damaged vessel so great that the sensible option is to sink your own ship? I assume that most scuttled vessels were crippled so that they could not move under their own power. With that being said, could a crippled vessel not be towed by another? For example, the [USS Neosho](https://en.wikipedia.org/wiki/USS_Neosho_(AO-23)) was crippled and kept afloat for four days before being scuttled.
Is it similar to crippled climbers on Mt. Everest, where if a climber becomes immobile, they are almost guaranteed to be lost due to the impossibility of being carried? OR is it possible to tow a cruiser/carrier/destroyer/frigate/etc across the ocean? Would chains or cables connecting the two vessels simply snap due to the immense mass of the two vessels tugging on one another?
If vulnerability is the issue (crippled vessel is a sitting duck), can a screen of defensive ships not be placed near the crippled vessel in hopes to protect it from being sunk?
If the stricken vessel being seized by the enemy is the issue, why? The enemy would have to figure out a way to bring the vessel back to their shores, which only goes back to my first point. Without understanding of the vessel and how it is built, chances are low they would actually be able to use it effectively. For example, surely if the Japanese captured an unmanned American carrier, they would not have the technical know-how in order to operate its systems. It would take a very long time for the enemy to reverse engineer it, let alone attempt to copy it when laying down new carriers to be made for the years to come.
This is a partial answer specifically pertaining to why disabled German U-boats in WW2 were scuttled prior to capture. There are a few main reasons why U-boats were scuttled in combat, and these carry over to other types of vessels as well:
Beyond the U-boat topic, large capital ships and (especially) merchant ships were often scuttled by gunfire or aircraft to prevent them from becoming a hazard to navigation. Collision is a major threat to all ships in all circumstances, but especially so in wartime conditions where ships are traveling without lights on. If the crippled ship is in a shipping lane or otherwise in an area where traffic is an issue, it must be dealt with so that other ships don't crash into it.
I'll touch on one of your points - capture by the enemy and re-use - since the other comments covered the other points fairly well.
As of the Second World War, several instances of enemy vessels being captured and pressed into service were still in living memory. While it's usually associated with an older era - Trafalgar, for example, saw the British capture a significant portion of the enemy fleet - the capture of capital ships had happened as late as the Russo-Japanese War of 1905. During the War of the Pacific in 1879, the Peruvian ironclad Huascar was captured by the Chileans and refitted in time to serve in the war against its former masters. More recently, twice in the span of a decade, the Imperial Japanese Navy had captured enemy capital ships and pressed them into service.
During the First Sino-Japanese War, the Japanese had captured a number of Chinese vessels, including one of the Beiyang Fleet's two battleships - Zhenyuan - and pressed it into service after a refit under the localized name Chin Yen. Notably here, Zhenyuan had been grounded on a reef and captured, while her sister Dingyuan was scuttled precisely to avoid such an outcome. And while this capture occurred at the end of the war, these ships would be employed to fill the gaps a decade later when war broke out with Russia. Chin Yen would participate in the blockade of Port Arthur and even see action in the Battles of the Yellow Sea and Tsushima. From there, she'd go on to be the heaviest ship supporting the last-minute invasion of Sakhalin.
And out of Tsushima, the Japanese would capture a number of other warships. The battleships Oryol, Imperator Nikolai I, Admiral Seniavin, and General-Admiral Apraksin were captured, and three other ships would be scuttled or otherwise destroyed to avoid capture. Even when ships were sunk, salvage by a victorious enemy wasn't out of the question - the Japanese raised and returned to service almost every major ship that was scuttled at Port Arthur - battleships Pobeda, Peresvet, Retvizan and Poltava and the cruisers Pallada and Bayan. Compare this with the Japanese fleet's strength at the end of the war - a mere four battleships - and you can see how significant this was. Japan was able to effectively triple the number of capital ships at its disposal.
Obviously, by the time of WW2, things were a bit more complicated. Reworking a captured ship for friendly service takes time and can be less than ideal. But a warship is a warship, and a "free" one can still be put to use in ways that free up the better ships for more pressing roles. In the case of Neosho, a fleet oiler is a tremendous asset to a fleet, especially when you're talking about either the USN or IJN attempting to project seapower over extreme distances.
And the Russo-Japanese War lay heavy on everyone's mind - particularly the Japanese, who based much of their strategic thinking off of that war. The Russian capital ships hadn't made it back into service before the end of the war, but the war in 1905 was brief. This was a long slog, and there was a very real danger of a captured vessel making it back into service to fight its former masters.
The US Navy had dedicated fleet tugboats that were responsible for towing incapacitated ships. Fleet tugboats had the power to tow any vessel in the fleet, were large enough to withstand any sea conditions, and had the range to tow fairly long distances. These consisted of the older Cherokee Class and the newer Abnaki Class. As far as how it was done, they would simply tie a hawser from the tug to the towed ship, much as it would be done today.
They would certainly want to recover any ship they could, but it had to be safe, logistically feasible, and economically worthwhile. The Neosho really didn't meet any of those criteria. This was before Midway, so the Japanese had a distinct naval advantage at that point. It would also have to be taken to San Francisco for repair. Repair facilities in Pearl Harbor had a long back log of work, and they had yet to set up forward repair facilities at places like Espiritu Santo and later Ulithi that could repair a damaged ship enough so it could sail to the mainland under its own power. It would also be several months before tugs would be forward based anywhere near the Coral Sea.
The Arikara was an Abnaki class tug that saw action in both Normandy and Okinawa. During the invasion of Normandy, it would mostly be tasked with pulling LSTs off the beach that were stuck, although it would also tow ships back to the UK for repair. At Okinawa it mostly towed ships damaged by kamikazes, usually destroyers, back to a repair facility. One such destroyer was the Dickerson, but after naval engineers in Kerama Retto viewed the damaged ship it was declared a total loss and sunk. Another was the Evans which took several hits from kamikazes and was towed to Kerama Retto, repaired and returned to action. Finally is the Longshaw, which had run aground and while they attempted to tow it free its forward magazine was hit by an artillery shell and exploded. The US Navy page for the USS Longshaw shows pictures of the Arikara attempting to tow it free as well as the moment it is destroyed.