1. None of the ~ two dozen websites I've bought from in the past year supports it (and those are already technical shops). And most importantly, Amazon doesn't support it.
2. None of the people I've wanted to send money to have it
3. Never heard of it; why would I trust it? (well, ok, they have some well-known clients, so that gives them some level of trustworthiness)
I am aware it's a chicken/egg problem, but as a user, I don't care.