The problem is that the entire field is driven by sales people with very few exceptions. The only objective is to make more money tomorrow, so they only think about how they can squeeze the market just a bit more... Like "Oh there's an empty spot on that page, put an ad there now!", or "Hey did you see those ads that cover the entire page? Advertisers love those... I want you to implement it on all sites asap!".
Ethics, morality, user experience, security and privacy concerns are simply not a part of the equation.