Because a good bounty manager is responsible for the reward threads are generally reliable.
Yes I agree with you. There are many people get mad of the bounty campaign because their effort was nothing after completed the campaign due to not get paid with their great participation, or in short it is a scam bounty campaign. With this we need to be careful in choosing bounty campaign that we are going to join to. First make a deep research of the development team members if they are legit in their physical identities and most importantly the community and bounty managers are having a good reputations and history of successful previous ICO's campaign. Maybe with this basis we can really get rewarded and less of chances to be a victim of false bounty promises of payments.