It is not like Amazon. Most people get Amazon Prime for the "free" shipping, and Prime with ads is a good value proposition, you get shipping but get a discount on the part that doesn't interest you. I don't get why tying a shipping to a streaming service isn't more controversial by the way, it is borderline illegal.
Oh, and by the way, ad-free is not really ad-free, you still have sponsored segments, but these are not under YouTube control.