When you've driven away your reader base, any profit you made while doing so will seem minor, compared to total revenues from keeping those readers happy and around for years to come.
Of course you can also view it as a major source of income immediately, and just ignore that it's driving away your readers. With the readers dwindling, you've lost leverage, and the advertisers are able to offer you worse and worse deals on the ads, which compounds with the dwindling reader base.
Scam ads are a choice that only makes sense in isolation. The advertisers are only your customers due to your reader base. You need to keep the reader base around.
It's a balancing act, of course, and as long as the optimization function of churn and revenue is trending positively it will remain. There are dozens of data scientists working on this problem. Taboola ads are at the bottom of pages away from the main content.
Sure, stand your customer base in a mine-field for some minor short-sighted profit. Implement this at your own peril.