GitHub got rid of their banners in 2020: https://github.blog/2020-12-17-no-cookie-for-you/ I believe there is also a lot of "cargo culting" where site admins copy what everyone else is doing without understanding the legal background.
That’s what happens when you add regulations to an industry of small players who can’t afford to spend time or money in understanding these things
I also think that it users don't mind the inconvenience too much. Complain, yes, but they are not really choosing a website that doesn't have the popup, over a website that does have. And so, businesses have no real incentive to change their ways.