In a realistically portrayed fight, a fighter who gets knocked to the ground tends to have a hard time getting back on their feet unless their opponent allows it. Not so in Video Games, which have to make this ability to return to action possible, or else the (NPC) opponent could make the game Nintendo Hard or even impossible to complete. If taking a single hit, when you can still take more, is functionally a game over, this causes every attempt to be a No Damage Run, and completely counters the point of even having defense at all, slower characters who rarely hit first, or many other game mechanics.