I think it will be more preferable to have rewards paid in bitcoin or ethereum in order to save bounty hunters from receiving blames unnecessarily.
I will say it many times already and will say it once more, the team doesn't have initial money to fund their project that is why they are launching an ICO to fund it. One thing more, they don't want to risk their own money into a project that is not 100% successful. We know that some of the projects right now are either scam or doesn't reach their soft cap ending in abandoning it.
All right. That is why for projects holding a bounty is the most profitable marketing in terms of costs. If successful, they will pay their tokens, the fate of which will be further decided by the dynamics of the market, in case of failure no one will gain or lose anything, except time, of course .