Not all links work with HTTPS, some can only be read or accessed via Http.

The way HN is moderated today to accept only quality content, in the similar way, HN can mandatories HTTPS. Then people will start porting sites to HTTPS soon. There will be a clash but it's for good.

HTTPS isn't a signifier of content quality, so mandating it would not be 'good' in any sense that's relevant to the community.

For the same reason Hacker News doesn't categorically ban articles behind a paywall, provided a workaround exists.

I wasn't either trying to correlate HTTPS to content quality. It was an analogy. The way it's mentioned in the Guidelines of HN, https://news.ycombinator.com/newsguidelines.html, that the submission should gratifies one's intellectual curiosity. In the similar way, HN should add in the Guidelines that it will only allow HTTPS links. Again, no correlation with quality and HTTPS. The way it's mandated is the suggestion.

My point was that unless it did result in an improvement in quality, there would be no reason to do it.

And as has been mentioned elsewhere, it would probably be a net negative for quality since potentially good articles would be banned.

Rightly said. Can we not push "good articles" running in HTTP towards transitioning it to HTTPS? Definitely we may lose those articles during that phase, but a probable security risk can be avoided. A thought.

Are there any use-case for http links on HN in 2021?

I normally don't side with less security, but yes.

Historical internet websites come to mind. These are posted from time to time here.

I noticed many Ham radio operators run their personal blogs with the name of their call sign on http.