Thye are not helping scammers if they knew that these are scams they will not promote it, they are not in a business of wasting time and effort and money, bounty campaigns are very few now, and bounty campaigns are like gambling they will only know if the project is a scam after the dev run with away, don't put the blame on bounty hunters they are victim also.
but the question is that they know that its a scam ? its okay if yes but the reality is that scams now are getting harder to detect .
didnt you see many hunters complain that they arent getting paid or got paid by worthless tokens . doing bounty does not involved money but only time and effort but the owner could have spend some money for promoting it and hiring some person like manager to organize a bounty .