I don't know, it seems to me like a search engine does aggregate customers. Aggregate means to put together, and having an easy way to search for the highest rate focuses the people who want that on whoever is at the top. Since there is predictably a pool of people like that, having them come together in some more explicit way wouldn't seem to add any value.

The highest rates are a lot higher than normal, (like 2%) and from banks that you wouldn't normally think of, so I don't understand where anything additional comes from. It seems like a projected free lunch from unspecified sources.