The issue here is assuming that the users of said sites are their customers. They are not.
When you are selling beef, do you worry about how the cows feel about it?
When you are selling beef, do you worry about how the cows feel about it?
If you don't care about the welfare of your cows they will not grow as large and you'll have less product to sell.
Putting that in more literal terms, if you damage the user experience you will damage user engagement and your ad revenue is going to fall.
There's certainly tricks to treat the cows poorly and still profit for a while but this sort of behavior has killed many companies.
To use an animal aphorism used in the context of Wall St, "Bulls run, pigs get slaughtered."
The point is users are ancillary, not the primary means of revenue. Whenever there is that mismatch, you'll have issues like this.