This is a pretty broad question - I assume you're referring to the 'blitzkrieg' with tanks charging ahead of the main body? Also this is obviously more early in the war when Germany was on the offensive.

Really the answer lies in the Battle for France (or the Sedan Campaign) where this style of driving independent armoured units deep into the enemies rear to cause a collapse was first used and successful. It would be repeated in Russia to mixed success due to the poorer road networks, poorer conditions of the roads, vast territories, and an enemy who would have the time/space to survive the initial onslaughts and learn from early mistakes.

The initial German plan was very much a rehash of the Schlieffen Plan (i.e. advance through Belgium) which the Allied plan would have met head-on and potentially created another deadlock which would be fatal for Germany. Manstein thought the plan was a poor one and continuously agitated for an attack through the Ardennes and punch through a gap in the Maginot Line. His badgering got him promoted to a command in eastern Germany (i.e. and out of the upcoming French campaign) but he got to dine with Hitler as part of his promotion and sold the idea to Mr. Moustache. At which point OKW was all over the plan and in fact we have one right here - just ignore the liquid paper over the author's name, it's definitely not Manstein. Nope.

So the idea was to run three panzer korps through the Ardennes and punch through the Sedan River defences which would get you tossed out of any army for proposing such a hairbrained plan. Imagine trying to run thousands of tanks, APCs, and trucks through just a few roads and the result is enough gridlock that even Los Angeles would say "damn son". Had the Allies paid more credence to their reconnaissance flights and bombed the roads they could have set back the German attack by weeks.

Belgian and French forces did fight hard delaying actions but miscommunication between the forces benefited the Germans. Then the Sedan River should have been a major impediment as conventional military wisdom said you need massive artillery support and that would've entailed a week of building up sufficient guns and ammunition to support a river crossing. The German plan was to throw the bulk of their tactical air assets to suppress the defenders enough to let the German infantry to get across and setup a bridgehead to get armour across.

Now German high command was very much still thinking conventionally in that the Panzer Divs would punch a hole in the French line and then roll up the flanks while the infantry divisions crossed. However Guderian and the other Panzer Korps commanders had a very different vision - they recognized that if they could push hard into the enemy's rear utilizing their mobility, they could sow panic and disorder and prevent the enemy from reconsolidating new defense lines. At this time the Panzer Divs were entirely motorized, in contrast the men in infantry divs marched and their supplies were on horse-drawn wagons. So disregarding all norms, Guderian and the others punched hard into the French rear and completely disregarded their flanks.

Again, this kind of maneuver would get you assigned to permanent command of a squad of potato peelers. But the Germans were moving so fast and the French were so disorganized that every time the French fellback to their next defensive position they found the Germans already there which necessitated another retreat to a position where the Germans had already reached... rinse and repeat. Many units never fought because French doctrine was to setup a contiguous defensive line and so rather than counterattack they kept retreating (French military leadership had a host of problems in the early war period). At the same time German high command was getting increasingly nervous looking at situation reports showing the Panzer Divs miles ahead of the army formations and completely unsupported - if one French thrust cut their lines of communication back to the bridgeheads then the tanks would run out of ammo and fuel supplies and be wiped out. There was an early attempt to reign in Guderian and he threw a (rightful) hissy-fit and threaten to resign so his commander came up with a fiction that he'd do 'reconnaissance in force' (force = his entire Panzer Korps). Guderian even stopped using his radio to command and used a wired phone to stop OKW from getting a fix on his position via radio triangulation.

This is a very long way of saying yes there was a very good reason the tanks (and motorized infantry, engineers, AT, and artillery) just raced ahead of the rest of the marching army. They accepted the risk of being cut-off and wiped out by flanking attacks based on the principle that if they kept moving quickly the enemy wouldn't know where they were to properly strike. They also recognized that this kind of attack would sow massive amounts of confusion as the French and English tried to setup new defences to stop the Panzers - who they weren't sure exactly where they were. The German plan however hinges on several key factors:

• Command of the air. Air reconnaissance would pinpoint the spearheads and their logistical trains and make them vulnerable to counterattack. The reliance on roads meant hitting the road net would dramatically slow down the armoured advance (tanks can go cross-country but it's much less fuel efficient, but the infantry and other supporting arms mostly relied on trucks which weren't great off-road and tanks unsupported are very quickly dead tanks).
• Good communications on your end and conversely bad communications on the enemy's side. The Germans embraced radio and this allowed commanders to maintain control over their units despite being separated by miles. Conversely the French didn't have as many radios and a preference for formal written orders meant many units sat waiting for 'official' orders and letting opportunities slip.
• Leadership. The Germans were aggressive and ready to take risks. They got inside the French OODA loop and took up residence (and ordered matching carpeting and drapes). It left the Allies constantly reacting to the Germans. Really French high command didn't win themselves any laurels with their performance.
• A good road net. This is a huge thing, if your Panzer Div is stuck using one road then any delay stops the entire advance. Any delay gives the enemy a chance to bring up forces to delay or halt your advance - and your forces are not concentrated but strung out in a column. Having multiple roads means your division can advance along several axis so that one blockage can easily be outflanked and its harder for your opponent to stop all of them. France had a really good road net that allowed multiple Panzer Divs to advance in line.

All to say it's an incredibly risky maneuver. The counterattack at Arras, although unsuccessful, scared the dickens out of OKW. A better organized and supported counterattack could have enveloped several of Germany's scarce Panzer Divs and severely mauled them before the rest of the army could provide support. It was something Germany had to do because a long grinding war of attrition with was something they were desperate to avoid. They recognized the threat of the French army and wanted to avoid another long bloodbath of trench warfare.