This is a valid point but.. advertising seems like a very inefficient way to solve that problem. In an ideal world, people would have knowledge of all available

This is a valid point but.. advertising seems like a very inefficient way to solve that problem. In an ideal world, people would have knowledge of all available products and services and also the ability to pick optimally among them. Something that could possibly replace the function of advertising would be an independent organization that would provide tools for picking the best product given your situation. And information channels for new high-quality products (i.e. there's a new restaurant in your neighbourhood).