You have a good point but at the same time if every projects start paying before bounty it still doesn't stop the fact that those coins can be worthless or scam, you can get paid of a token or coin that won't be useful for anyone,
Thats true even the team pay the hunters upfront nothing will change if these tokens are just shitcoins in the end. Its another display in our wallet right? Otherwise this is not the case however we know its not easy to determine a legit projects, it would be better if they pay the half of rewards in btc or eth and the rest in their own tokens, thats better but not possible for alts bounties to happen.