Unfortunately search engines typically also own the ad networks.

You know, now that I think about it, that sounds like a really good reason to file an anti-trust suit. Search engines have a clear conflict of interest to prefer content that uses their ad network. Search engines should not have a preference for a particular ad network, but they almost certainly do and that harms the consumer.

add to that that google turned to crap nowadays and just pushes meaningless bot generated content in the top pages... it's getting almost impossible to use it to find stuff. not sure about other engines because I only started recently being search-engine-curious, so no idea how they were like before