Actually in D20 and variants, a 20 is automatic hit and 1 is automatic miss, only in combat, and I think they're just normal rolls in skill checks and probably saving throws. So on a natural 1 you just add 1 to whatever base bonus you have, and if 20 isn't enough to lockpick something then it just doesn't work.
Neither is a critical, technically, that's actually a function of the threat range (all threat ranges just happen to overlap with the natural 20). There's a subtle distinction... yeah for all intents and purposes "natural 20 means critical threat" could be said, but it's an oversimplification.
No such thing as a critical miss in RAW. Even as a house rule, having 1 being automatic critical failure is too much, you'd have to "confirm a miss" or something. Also it penalizes martial classes with multiple attacks per round (a high-level warrior with 5 attacks per round would get a critical failure every 4 rounds
).
Also when confirming, natural 1s or 20s are irrelevant per RAW, if a roll of 20 + BAB +bonuses would miss, it means you can't crit that target with your current BAB, and you can confirm a crit even on a roll of 1 + BAB+bonuses.
So yeah. Crit failure is house-rules. Because watching a fighter hit himself is hilarious apparently.
EDIT: Right... about removing auto-hit/auto-miss... well, it would just mean that it's impossible to hit some creatures/NPCs with enough armor because levels.
In some games this works, Fate for example, you NEED enough bonus to beat defense (both roll but if the target's defense is 9 ranks above your attack - not exactly very plausible unless you burn advantages/points - you just can't hit. Unless you burn your own points. Realistically nearly everyone is in the 0-4 skill range, unless some kind of giant monster that must be killed using teamwork or other tactics. But I digress, there just isn't an auto-hit.
EDIT2: Not sure why I posted all that rant about criticals, I'm just sleepy, it's time for bed already. Also automatic success/failure also works for saving throws, just not skill checks. I guess I just wanted to point that natural 1 automiss is not a houserule, critical failure is.