It is something about the shape, but there is something about a vessel sink that makes me hesitate to use it – though I still do. Maybe it is that the lip is usually too high (thus awkward to get hands in there), maybe it is that they look more like art than a functional object, maybe it is that it seems like a shame to get them dirty.
But the last thing you want to do is discourage men from washing their hands. 🙂