Don't underestimate the argument of "just to be on the safe side". Someone running a business who doesn't know a lot about cookies will often just put a banner on as an easy arse covering mechanism even when not required.
Or they had their site developed by an agency and the cookie banner is just part of their standard scaffolding for a new site.
Let businesses who don't know what they're doing be outcompeted by businesses who know what they're doing.
Perhaps someone could publish a clear A/B test on how many views/conversions you lose by having a cookie banner?