> They take valuable resources from legitimate functionality
Including our own. Ads are designed to pull our attention to them and away from what we want to be focused on. The goal is to forcibly embed something in our thoughts and/or feelings. Maybe it's a lie, or a false association, or an impression, or a fear. One way or another ads seek to manipulate us and like it or not we are all changed by them. We'll have a cure for cancer long before we get a cure for advertising.