Why should they accept bitcoins? Aside from you just wanting them to, that is. Who is unable to pay them in a currency they accept but who would pay them in pretend internet coins? Do even five of those people exist?
You're right in your first post, this is a complete waste of your time. But that's not an uncommon theme with bitcoiners.
Actually given how kids are shut out of a lot of net commerce due to not being able to get a credit card and such, but may just have a decent graphics card for games and time and knowledge to figure things out, I bet the number that would do this is far more then you would suspect. It also is smart marketing to get kids used to bitcoins and the idea they have value.
^This!
A lot of kids that doesn't have their credit card and whatelse are able to use their GPU to mine without problems and will then buy games and other things with bitcoins
Sure they won't make thousands of $ per month via mining, but even 15$ is enough to pay a MMO, so they can and will