Ad programs like Google Ads pay off on page views. The more people visit your site, the more the ads are seen, the more money the site makes. And it's not just web pages. The phone apps - specifically the games - have some really strange ads playing before you can get to the next level. Of course if you pay a monthly fee, you can play ad free.
Social media is another place where ads can overwhelm you. Unless the owner changes rules, decides to fire workers and essentially creates a place that people decide to stay away from hence no views, advertisers pull out, and as a result no revenue.