Overwhelming people with ads, targeted or not, leads some folks (me, for instance) to block them all (thank you Brave!). Advertisers also fail to understand that some people aren't hyper-consumers and are *never* going to click on that ad anyway (me again). On the rare occasion that there's something I'm in need of, I do my own research to determine what to buy and where to buy it. If you're throwing ads in my face, I'll consciously discount your product/service on the spot. With the Web being what it is, put your $$ into your product, not ads, and let word-of-mouth on the 'net do the rest.
Yeah, I’ve never deliberately clicked on an ad. Mis-clicked, yes. Although I suppose gaming a search engine to improve your ranking might be considered ‘paid advertising’, and I would have clicked on those.
But I guess enough people do to make it worth their while. It might also have a subliminal effect like TV ads, except you have the advantage of only targeting people that might be interested in your product in the first place.