Bounty hunters are requesting to get paid through Bitcoin and Ethereum or other tradeable coins so bounty hunters will not dump their token when it hit the market, thereby protecting its price.
But they don't want that because they do not believe that their own token will have value or demand when it hit the market

and that's actually what's happening
That's one of the reasons I can think of if you have more post it here.
That might be true, but it is actually not the bounty manager decision.
Usually the team themselves are willing to pay bounty participants with their token, not with top coins.
Some bounty managers agree with that, but requiring to pay bounty manager in btc or eth.