Advertising these days is less of a way for websites and services to make free money.
Of course websites and services that serve ads will deny this vehemently because advertisers who become aware of such practices (typically known as click fraud) will cut off those websites from ad revenue very quickly and stop serving ads there.
The idea is to trick the advertising companies into thinking that we are there and we are watching, and we care, so that they will pay money to the website to display ads there.
The point is that people think that it’s effective. It’s the illusion of security, which does actually keep some of the more stupid spammers and bad actors at bay. It doesn’t stop the ones that are determined though, nothing does.