> However, the real reason these irritating dryers are popular is virtue-signalling: they're a way of announcing to everyone that you washed your hands

I don't see how that works. In most offices I've worked, the toilets were situated far from the desks, where nobody could hear the hand driers or see who was coming out of the can after the hand drier had gone off.

Also, I seriously doubt that strangers in the public loos look up at me and admire my determination not to spread my germs around. Public loos tend to be in places were people have very different things in mind: catch their train, finish their beer, etc.