Ask HN: Why browsers don't verify cheksums of downloaded content?

Sometimes linked content from download pages gets compromised. I was wondering why there is no user friendly way of verifying checksums. Or maybe I am missing something?

It would be nice to have some HTML markup so the browsers would be able to do verification automatically. But making browsers' download managers compute most popular hashes after downloading and displaying it somehow for many would be enough. This simplified solution would make me take a peek to see if checksums look right, it would be much better than what I do now - I only check hashes after downloading from suspicious (to me) websites.