Because they wear more visible signature/ads that's why most of the campaign manager or the company choose higher ranks since they get more better exposure than hiring low rank. But don't feel bad about it since there are generous companies open a campaign for jr member rank and up so maybe you just need to wait for that opening since for that maybe you could join then earn.
Wear a bigger and more colorful signature is big advantage of higher rank members. If two members, low-rank and high-rank, write two posts with same quality, a higher-rank member will be more helpful for a company.
High-rank members don't always make good posts or better posts than low-rank members but it is responsibility of campaign managers who are hired by companies, to filter applicants and choose best ones for the campaign and company.
But usually the decisions towards choosing ranks will depends on how the company and the manager discuss about that situation and the final say will always go to the company if they want to include low ranks or just choose high rank for good visibility of their ads here.
Usually difference between Hero member rank and Legendary rank is small and some campaigns consider Senior member rank as same as Hero/ Legendary rank and give same pay rate for participants.
