One is a response to a request, while the other is unsolicited and usually explicitly undesired.
A better analogy to sending resumes in response to job ads would be a salesperson describing the features of a product I've gone into a store and explicitly asked for information about.
> Regarding companies creating a role, would that imply that ads as a response to a search would be acceptable?
Most of my searches are not for products, so it doesn't make sense for Google etc to shoehorn ads for products into the results. If I'm searching for a product, then yes I want to see some ads for those products.