It's true that this exists but there are complications – for example, rel=prefetch has no JavaScript API so you either need to put rel=prefetch for all of the top results or do something hacky to trigger it for only the link the user hovered the mouse over before clicking, etc.
There are also privacy concerns – e.g. the remote server could set a cookie in a response without you ever visiting that site but if you disable cookies by default users will have to refetch the resource anyway if there's any session state involved in page generation. You also have issues like companies wanting to distinguish between traffic from actual page views and the prefetch mechanism.
That's not to say that the answer is AMP — e.g. since it puts so much render-blocking JavaScript into the critical path prefetching is often just canceling out that cost – and it's sad that the marketing push has made the discussion of alternative performance improvements unnecessarily contentious.
