Projects team and devs started behaving this way when hunters started cheating by creating multiple accounts and getting caught through wallet pooling. This has destroyed the credibility of the innocent ones. I do believe alot of projects are taking advantage of this to not pay even the good ones which is unacceptable. Escrow has helped with this but still team has the last say when it comes to distribution. It's good that bounty managers are also filtering out cheaters to minimize such act.
Not a big issue many people is looking for those cheater even tagged them if proven that they cheat one of the bounty campaign . The reason why they don't pay is because they want to pay participants in the first day they starting it.
There is always a way to find those cheaters but not giving them payment is a problem since not all of the participants cheat.
If a project doing that they deserve to be tagged and even giving a flag for the project. it will destroy the reputation of the project but,they deserve it its the result of not giving the right payment for those participants that completed the job.