I'm sure you know that when you use Google, search results are a side effect which is used to draw you to use Google, the main product being provided are the ads.
We're talking about the user's perspective here, not Google's. For the user the search has one purpose, and that isn't looking at ads. Just like nobody opens a newspaper to look at them.
The point was that nobody really needs advertising to learn about available products. Google search stays just as useful if you block the ads, the other way around nobody would use it.
I think that's too narrow a scope you are putting on people who do searches. I in fact have searched on Google for ads, when I was looking for car insurance. I'm sure other people have searched for ads as well, I can't be the only one.