I don't really have a stance one way or the other, but I don't think people just produce content for ad revenue. A lot of people produce content just to get their name out there/increase their branding, an incentive that AI summaries undermine. There really is no motivation to produce something if it is just going to be regurgitated by AI agents. And, yes, I know they cite sources in their responses (at least Google does), but that is a pretty paltry substitute for actual traffic to your site.