No, what you mean is YOU use it and you’re assuming most people use GitHub the way you do. GitHub is first and foremost a platform for GIT. Git has nothing to do with releases or file downloads per se. Time spent improving the releases UI is time not spent doing other UI improvements. If you need more proof that it’s not worth it to spend time on the release UI, just take note of the fact that GitHub is not spending time on the release UI. If everyone was using it and it was deficient, do you really think that would be the case?

It makes sense from a pure UX perspective. But of course the real goal of GitHub is to make money, and their paying customers are mostly corporate entities using it for enterprise development. Unless those companies decide that a download button/better release feature is desirable, it's not likely to happen.

Most corporations tie GitHub into their own build system so such a feature isn't likely to be considered useful. They pay for GitHub to reduce development costs, which is why GitHub spends so much effort on analytics and the dev experience instead of open source/public users.