In addition to the rationale outlined by /u/The_Chieftain_WG , there was an additional problem for a Kriegsmarine carrier: planes. Carrier aircraft often have different requirements (undercarriage, fuselage strengthening, landing equipment, etc.) that add to both complexity and cost of carrier aircraft. Getting funding for procurement of these aircraft was quite difficult in the 1930s, and the presence of a separate air force added more difficulties. In Germany, as in the Italian Regia Marina, the French Navy, and British Royal Navy, the air services saw the presence of a separate naval air arm as a threat to their institutional base and a rival for funding. Independent air services were able to portray themselves at the forefront of modern technology to civilian decision makers and jealously guarded their monopoly on procurement and designs. Of the national navies who had independent air forces, only the RN was able to overcome this institutional friction to produce a healthy naval air arm, and even there it was compromised. Early war RN carrier aircraft were not as advanced as their RAF equivalents, and the service later had to make do with converted land-based aircraft (Fulmar, Sea Hurricane, and Seafire) and lend-lease aircraft. It was only by the later stages of the war that it received purpose-built indigenous carrier aircraft that were cutting edge. Navies that did not have to compete with a separate service like the USN and IJN had a much easier time getting funding via established naval procurement networks.

The plans for Graf Zeppelin's air group illustrated the problems latent in these type of interservice rivalries. Göring was adamant that the carrier's air group would have been composed of Luftwaffe pilots and its planes would be converted Luftwaffe types (the Bf-109T and Ju-87C) which were not really adequate for frontline service in 1941. There was very little attention given in the German aviation industry to a next-generation carrier conversion, let alone purpose-built carrier aircraft. This sorry tale was reflective of KM's strained relationship with the Luftwaffe in the Battle of the Atlantic One of the larger problems of the KM during the war was its poor coordination with the Luftwaffe's coastal units and the relative disinterest of the air service in maritime operations. The FW-200 emerged as a coastal strike/reconnaissance aircraft largely because of local initiative. When the balloon went up in 1939, the Luftwaffe found that it lacked aircraft with suitable range to patrol the North Sea and later the Atlantic. Consequently, Lufthansa's Fw-200 was the only aircraft in Germany's inventory that could meet these requirements. The Japanese had expressed interest in a militarized version of the Fw-200, the Fw-200 B V11, which had a gondola and provision for bombs. Hauptmann Edgar Petersen, an officer of the X.Fliegerkorps (the unit tasked with maritime strike), saw these versions of the Fw-200 when he visited Focke-Wulf in September 1939 to ascertain whether or not civilian aircraft could be used for this role. Kurt Tank showed Petersen the Bs intended for Japan and assured Petersen that production of a militarized Fw-200 could start very quickly. The RLM was relatively ambivalent about impressing the Fw-200 into military service, but there were few other alternatives.

Given these interservice headaches and the lack of any real need for carriers in immediate operations, it is surprising that development of Graf Zeppelin proceeded as long as it did. Getting even converted aircraft for naval service was a chore, so as delays took place in the carrier's construction, it was becoming increasingly clear that it would be a carrier with no planes. Hence carriers had few champions in the KM and carrier development slouched along as a means to keep abreast of naval developments for the postwar period rather than something for immediate use.

Well, they tried. Graf Zeppelin was launched in 1938, but never completed.

If you think about it, though, what purpose, really, would a carrier have served the Kriegsmarine? CVs have two main purposes, power projection, and fleet security. The Germans had no particular need for the former. Any place it was interested in generally was within range of land based aircraft.

More importantly, though, they considered the CV to be an escort/adjunct to the capital ships. This was not an unusual philosophy at the time. However, there were competing priorities for steel and manpower, and the CV was never really at the top of the list. The capital ships were getting sunk so there was nothing to escort, arguable exception of Tirpitz which generally stayed within range of Norway air cover anyway, and the UBoats seemed to be a more promising line of attack in the North Atlantic than a single division floating around the ocean trying to avoid being met by a significantly more powerful enemy surface force.

So, the upshot of it is that either the Graf Zeppelin was a 'pride' project more than something with great military worth, or it was just overtaken by events and might have actually been a useful consort to Bismarck had the war started a couple of years later. Not that it would have mattered in the end. The RN and USN would have still ROFLStomped it.

Sorry, but your submission has been removed because we don't allow hypothetical questions. Please feel free to rephrase the question (dropping the second part) so that it does not call for such speculation, and resubmit.

You can find a more in-depth discussion of this rule here.