I can say 100% that 60% of all bounty is a Scam. The reward for them is either given and the tokens will lie on your wallet forever or do not give at all. Then what's the point of doing this ?
This most times happen to airdrop, because so many of the bounties i participate in end up well. Although, i cannot deny the fact that there are scam projects which run scam bounty. This is more reason you need to always do some research before investing or participating in the bounty of any project. Ask questions where it is needed so as to be clarified on some things.
Then some projects these days are just waiting for the market to get better before listing.