Yeah, and the advertising market is only so big. Showing a user hundreds of ads still only makes them buy maybe one product they don't actually need. The profits from that one product are the maximum amount of money to pay for all those ads.
So, if Google shoves more ads down our throats, that means other companies get less money for the ads they show and so have to increase the number of shown ads, too. Even though this still likely won't make users actually buy more products.
It's an arms race and the loser is the user just getting thousands of useless ads.