Opinions vary. Mine is you should never use an admin-level account as your day-to-day login. OS X may have features that protect you from yourself if you don't, but it's still poor practice and explicitly separating admin from regular users helps enforce the point of what you're doing.
I agree with you. There are many times I would have toasted my system and had to restore from time machine were it not for file permissions while running as unprivileged.