A lot of people actually want to be sold to.
But the good ones do.
With a knife, you can stab a person to death or you can cut onions to dinner.
Are you confused between newsletters/marketing and actual spam maybe?
I always receive a ton of newsletters. Never once have I signed up, I always uncheck all sign up prompts and always immediately unsubscribe if I receive one.
Even then, immediately after any sort of purchase I get resubscribed. I’m convinced that most shops completely ignore all user choices and resubscribe everyone to all mailing lists after purchase.
You'd be surprised how many people don't understand how, say gmail works and just start using an address they never signed up for and now I'm seeing mlb.com receipts for purchases, or someone's student loan paperwork.