I've got small (but mighty!) hands and have never been able to comfortably use my thumb for chording. On the other hand (no pun intended, alas), after a week or so of practice many years ago, I never had problems with barre chords. I suspect it comes from being subjected to the wisdom prevalent among many St. Louis musicians in the 60's and 70's when I was just learning, that if you played an F any way other than a barre, you weren't a 'real' guitar player and weren't to be taken seriously. I guess you'd say that peer pressure forced my hand.
...Or not.

Sean