Small question about JB.

What is actually the purpose of this "currency"?
Is it just seen a play money? Just wondering because it is odd to give play money for level ups (of course there are also other rewards but JB is a part of it) .

Maybe I am missing something here, that's why I am asking. 

JB is a free onsite token. You can't buy them or sell them. They are free credits you can use to test out the games. We make this very clear.