Rolling a 10 can be good. It's usually enough to get you through moderately difficult encounters - picking a lock with thieves' tools; chatting up a whore at the local tavern; hitting a peasant who has no armor.
But a Natural 20? That's when the good stuff happens. Critical successes. And, if you have a kindly GM, you can change the world in which you are playing.
Now, that's what *we're* all about.