There seems to be an assumption that hoods=breath play when really they don't. They aren't even really blondfolds necessarily, unless you want them to be. The point of a hood is to dehumanise a sub - remove the face and the sub becomes something less human and therefore more open to abuse. Things like blindfolds, gags and breath play add to that but are by no means essential. My leather hood has open eye holes and an open mouth hole (which cannot be blocked easily). You can add a blindfold to it easily enough, you can also add a gag (including a gag with a tube that can be blocked for breath play) but the main reason I wear it is because it triggers off the submissive feelings in me (and presumably triggers dominant feelings in a Mistress...)

Sensory dep play is also an element of play possible with hoods - ear plugs, blindfold etc and the hood itself adds an extra layer of darkness to the situation as well as removing the sense of touch from the face. Can be scary but that is what the trust is for...