@rameshgupta Search engines somewhat given the lack of alternatives, although there is some without any ads.
Email services there's a ton of alternatives, typically including the ISP you're already paying for, same shit for blogs.
Social media? Not really applicable for the Fediverse, although it's more a mere network than media.
Maps? OpenStreetMap doesn't runs on ads.

And this can go on and on. Advertisers aren't needed, they just are manipulators as a business.