You missed that key line. It may surprise you because you personally don’t do this, but regular people love signing up for email newsletters.
This is very different from email sent unexpectedly when you make an account somewhere. The OP was clearly talking about a list the user has asked to receive.
These tend to have fairly clear unsubscribe links in the footer.
The one exception —again, just in my 20 years experience doing this crap— is when you pay them, eg "10% off your first order when you subscribe to our newsletter". This is still more coerced consent than informed, but better than most subscriptions.
We get that you don't like marketing email, but plenty of people do.
I also regularly walk clients back from doing exactly the same thing. The perks in marketing don't give a flying French Fancy what the law is. They care about absolute volume.
I did a little exercise last year, took a screenshot of every order form I submitted. I reported a dozen companies to the ICO last year, with documented examples of companies wilfully ignoring GDPR regulations.
Yeah, I'm also fun at parties.