I wrote a post on the "witnesses rule hive look they are also getting paid on dao" subject:
@howo/some-information-about-the-hive-previously-steem-proposal-system-sps-steem-dao-hive-development-fund-hdf

tl;dr: witnesses tend to naturally be paid on he dhf just because they are often devs and generally have the trust of the stakeholders. It's not because of a conspiracy thing.