At one time I had two dogs registered as therapy dogs through an online service (no longer available) *and* my psychiatrist wrote a letter to support them as therapy dogs after she met them and saw how well trained they were and attentive to my needs.

Only one of those two dogs are still alive.

Having my dogs certified as therapy dogs allows me to take them places they wouldn't otherwise be allowed to go, and it waived the deposit for them on my apartment, too. Of course, I need them, so that's the biggest benefit of all of having them registered!