There are some reasons why some persons will not be paid during the distribution of coins, this could be evident due to the failure of the bounty hunter in adhering to the aformention  rules and regulations stipulated on the bounty page.
Firstly, When a particular bounty requires a proof of authentication and he fails to submit his name, and other required particulars on the bounty thread.

Secondly, when a bounty requires KYC and a bounty hunter fails to participate.

These are many but a few to mention.