Instead of unsolicited ads why would it not work with targeting people actively looking for things only? Right now I’m researching a product I’m about to buy,

Instead of unsolicited ads why would it not work with targeting people actively looking for things only? Right now I’m researching a product I’m about to buy, because I have an actual need. In the process I consult various sources listing and comparing products of that category. Allthough most of those sources can’t be trusted to provide unbiased information, I’m pretty confident the sum will give me a pretty good overview of the search space.