First, do the math and you'll see these companies are highly under-valuing your time. Take the price difference between an ad-free plan and an ad-supported plan, and divide it by the number of hours per month of ads they'll show. It usually ends up being less than $1/hour. That's how much they'll discounting the service to pollute your brain. My time, especially my leisure free-time, is worth way more than that.
Second, ads are particularly poisonous to kids. They don't know how to differentiate between content and ads as well as adults, they often can't tell the difference, and the ads are particularly effective on them. It's really apparent this time of year around the holidays. My kids who never see ads on TV have wishlists that are, for lack of a better term, basic. They want "a truck," "more books," and "a doctor kit like at school." Their friends who have cable tv and thus watch ads at home have much longer and more specific wishlists, like they want the "Hotwheels City Hauler Ultimate" and the "Paw Patrol Rescue Mission Under the Ocean Playset." There is also a difference in how they react if they don't get the exact toy on their wishlist. My kids really don't care, because their wishlist was not specific to begin with. They're not disappointed because any truck and any book is what they wanted; whereas their ad-watching friends get really upset if the Hotwheels or Paw Patrol whatever is not the exact one they wanted. I'd rather have no TV at all than subject my kids to that.
And all it takes is a few bucks per month to rid my home of ads - that is probably the best money I spend.