Earlier quoted context omitted.
But they would earn more money from regular ad revenue, presumably. You're painting a rather bleak picture -- that the majority of creators/influencers' content is advertising. If that's the case, I'm not sure why Youtube/Instagram should also tolerate that -- it's basically spam on their platform they haven't curated through their ad network.
Brand deals are the majority of their income, but not the majority of their content. This just means the platforms aren't paying very much, since the platforms are advertising on _all_ their content and yet creators are managing to earn ~80% of their income through brand deals on a tiny fraction of their content. 58% of creators post 16 or less sponsored posts a year, and those with more followers post even less[0],…
Except if they believe you are not advertisement friendly content.
Like any discussion or educational material about any touchy topic gets not ads (and there are a lot of such thinks).
YT accidentally mistaking a think you sayd as a black listed swear word (even if you didn't say it and are not even speaking in the language its from and it just sound similar) => No Ad Money.
Politics => No Ad Money.
Covering Covid related thinks => No Ad Money.
Covering local news including violence => No Ad Money.
etc...