It works pretty well anyway, they have some sort of request queue management so that if you don't pick up pretty quickly it will try others, and from the outside looks like they probably try multiple people anyway.
So if you get a notification and you are available, great. Otherwise someone else will get it.
Most problems that people encounter are synchronous. I cannot even think of a single scenario where identifying things in a picture would be useful to anyone after the fact. It's not surprising that they don't offer a service that wouldn't be useful to anyone.
Makes total sense, but I thought volunteering answering some questions about photos people upload there when I have some time to spare.