i don't think it has anything with believing in the future of their token because the creators of these tokens know better than you and i that their token is useless and worthless.
the only reason why they pay in their own token is because it doesn't cost them anything! if they wanted to pay in bitcoin for example they would have to spend money and buy bitcoin and then pay people. but when they pay in their own token, all they have to do is just create them out of thin air with no effort or cost!
I also think so if they prefer to pay with tokens because without any fees. so now, payments with bitcoin or ethereum are starting to be rarely done by bounty hounter participants, maybe the team still wants to hope that if their tokens can be released in the public they don't think about the price.