If, for example, the number of participants for certain campaigns is not limited and the project is already relatively well-known, then the reward is accordingly low. The best example for me is Eventum / Verity. The bounty rewards were very low and therefor a lot of bounty hunters complained in the telegram channel. However, if one of those who complained there would have read through the terms and conditions and calculated the stakes, it would have been clear from the start that there would be very little to get at that bounty.
So who has to be blame them? That's the problem with bounty whores in this forum. They really don't read, they spam and then later they complaining that the project or this community is not fair to them. LOL. If they have at least learn to read and understand how everything works here in the forum, we won't see thousands of spammers 'invading' bitcointalk everyday, or at least bounty managers rejecting those spambies.