LogFAQs > #882389298

The benefit of a natural 20 is automatically hitting, no matter the AC of the target. It can also lead to a critical hit, but you have to confirm it (hit their AC again, doesn't have to be another 20).

This is a GOOD thing. It makes critical hits less common (note with some weapons and feats you can easily get the critical hit range down to a 15-20 on a d20, not every attack only threatens a crit on a 20), and less randomness is better for players. Because criticals are very devastating (some are even 3x or 4x as powerful as a normal hit), and just by sheer probability, player characters are going to be crit. A lot.
Non-player character enemies "exist" for one combat. Player Characters are there for EVERY combat. Countless attacks will be made against them, you really don't want a significantly high chance that any given one can kill them by sheer dumb luck.