In my time with it, about ~20 years ago, it had a lot of nice features for instance hg came with a web server/interface out of the box.

I liked too. It was `hg serve` [1]. Instant web interface and an easy way to share the repository with other people (assuming your computer was accessible from the LAN or Internet).

[1]: https://mercurial-scm.org/help/commands/serve