That's probably true. But it would also result in a lot of unfun gameplay. "Someone died, wipe it up." Again and again.
Combat resses are a "catch-up mechanic". These mechanics allow players to recover from a mistake and keep going. Without these mechanics, game outcomes have the potential to be unchangeable. As soon as one side gets an advantage, they ride that advantage all the way to the end. If you fall behind early, you can never catch up and win.
Think of chess. You can often predict who's going to win right from the first exchange which results in a loss of piece advantage. Someone nets an extra pawn, the odds in their favor skyrocket. Sometimes the losing player can mount a comeback, especially if she is more skilled, but it is rare.
In my opinion, having good catch-up mechanics is important element in making games more interesting and the outcome more uncertain. A lot of the problem with MMOs is that catch-up mechanics are hard to create, because invariably they get woven into regular play, rather than being reserved for times when one falls behind.
Think of most damage reduction cooldowns. Or feral/moonkin druid Tranquility. Tranquility used to be a great catch-up mechanic. If things went south, your feral druid could shift out of cat form and Tranq, stabilizing the raid. But now many raid teams incorporate non-healer Tranquilities into the healing strategy, and use them to buttress the regular healers at specific times.
Other catch-up mechanics in WoW include Lay On Hands or a rogue's Evasion. In an ideal world, you don't need these abilities. But when things start going bad, they're golden. I'm sure we've all seen a rogue Evasion-tank a boss for a few vital seconds.
Without catch-up mechanics, every mistake means that you have to restart. This doesn't result in a raid which doesn't make mistakes. It results in an increasingly short-tempered raid.