"Pay to have no ads" always seems great from a consumer perspective, but terrible from the ad buyer perspective. The people who would buy google premium are the people ad buyers most want to advertise to.
Widget Salesman: "I'd like to buy some ads for my widgets"
Google: "Cool. Some users won't see them."
Widget Salesman: "Which ones?"
Google: "Only the most-engaged ones with the most money."
Widget Salesman: "..."