Subscriptions and ads have gone together like peanut butter and jelly since the print age.
If you subscribe to The New York Times or Cosmopolitan you have qualified yourself as being interested in the subject, attached to the brand, and not hopelessly penurious. An advertiser would rather pay to get a message in front of a paid subscriber rather than anyone else.
One time I rented a unit in working-class neighborhood for 6 months and not surprisingly the amount of junk mail was half what I was used to.
Just look at how advertising is creeping into premium streaming services.