One definite advantage is the chance of slipping when climbing is nil.
pros climb a lot and i can tell you from experience that the pain of falling over when climbing in flats is much much more than failing to unclip..
Originally Posted by Colnago Mixte,20499688
I honestly think there is a rather substantial mechanical advantage to being clipped in, but if you don't use it, I suppose you might as well run flats.