The are two type of bounty hunter. First, is people which sell their token immediately or exchange to ETH because of many reason. The number two is people which hope that their token from bounty can got better price or even rocket to the moon. I think that FIAT reward are suitable for type one but some people too want to hold their token too. Also there is only few bounty that really paid with FIAT.
I very rarely go to projects that offer dollars during the company's Bounty, not steaks, as in other cases. Such company bounties give me confidence.