The advertisers are likely not measuring the right metrics so they may not even notice. Sketchy things like this would increase their clickthrough rate, but lots of those users would drop off at the start of the funnel and not progress past the landing page. Many advertisers don't properly measure funnel metrics end-to-end - how many people click the ad, then how many of those people view an item, then how many of those add the item to their cart, then how many of those get to the checkout, then how many of those actually buy the item. Users drop off at each point in the funnel and it's important to know where to measure how effective your ad is.
The advertisers are likely not measuring the right metrics so they may not even notice. Sketchy things like this would increase their clickthrough rate, but lots of those users would drop off at the start of the funnel and not progress past the landing page. Many advertisers don't properly measure funnel metrics end-to-end - how many people click the ad, then how many of those people view an item, then how many of those add the item to their cart, then how many of those get to the checkout, then how many of those actually buy the item. Users drop off at each point in the funnel and it's important to know where to measure how effective your ad is.