High-ranking members care about their reputation a lot because they worked hard to build this account on the forum, while Newbie members don't care if their reputation is tarnished.
Yes, I agree some projects will allow bounty managers to hold the tokens or escrow them, I read in the past where a bounty manager run away with the token that he was holding for the bounty campaign because the manager was lower rank, I don't want to downgrade lower ranked members but they have to work their way to reach a level of trust and prove their honesty in being a campaign manager, the only way a newbie become a campaign manager, is if he is part of the team.
Sometimes if a small company wants to run a campaign, they would make a new account on this forum and then run the campaign instead of hiring an manager who may be expensive for them. This is acceptable in some cases provided the campaign is honest and do not want to scam the bounties hunter / Signature participants and at the same time want to save some campaign management cost.
However, the drawback is that these newbies can easily scam the participants as they have nothing to lose expect the newbie account being marked as scammer and also their project being getting a bad name, which they rarely care as they make projects to earn quick money and then move on the the next one.