Sometimes the dev/team prefer to manage their own bounty hence they are creating an account here to personally handle it. There are also some bounties managed by newbies but still paid their participants at the end of the camapign, well its an advantage if the manager is a reputable user here but I think it still depends on the project itself. If you have doubts read their white paper, roadmap visit their site and the team behind the project.

As I said newbie manager is not an indication if the project is a scam, its better to research about the project first so your effort wont be wasted incase you decided to participate.