Here's how it goes down:

The punishment for rolling a 1 is that you miss, regardless of modifiers. It's entirely possible, if your bonuses are high enough, that you could still hit if a nat 1 didn't auto-miss. Therefore, the auto-miss is a punishment.

Compare that to a nat 20. With 5e's bounded accuracy system, enemy AC rarely goes past 20. That means that, unless your attack mod is a negative, a nat 20 is pretty much guaranteed to hit against all but an insignificantly tiny number of enemies (and even then, if you're anywhere near the level to be taking those on, you should have an attack bonus high enough to hit with a 20). So, a nat 20 auto-hitting isn't really a benefit. That's why you get extra damage on a critical hit, because otherwise a nat 20 wouldn't have a benefit, practically speaking.