I disagree. If you're falling off, either you a) have no balance, b) can't read a horse, or c) aren't paying attention or are acting like an idiot (and are thus violating every law of horsemanship).
I will, *cough*, on rare occasions, fall victim to the latter. Which generally involves something along the lines of trying to hop, bareback and bridleless, on the spooky mare on a windy day in the middle of the pasture with loose horses while carrying a handful of halters and a feed bucket. That one did not end well. I was picking grass and dirt clumps out of my underwear all evening. Ahem.
But I was also acting like an idiot, far from "doing something right." Good riders don't fall off.
Getting bucked off and bailing are two different scenarios. The former is justifiable if you've got a real bronc (but the rather valid argument could be made that, 9 times out of 10, a good rider can prevent a bucking episode in the first place). The latter comes into play if you've got a terrified colt or something and there's no good way to ride out the scenario. An emergency dismount can save you from paralysis and also prevent bad things from happening to your mount in his terror.