There's plenty of media/webpages I'd love to "save offline" on WiFi so I could then later access them without having to pay for mobile data (or access them at all on flights/road trips through areas with no phone service)
(Note that I am aware that for many pages you can, in fact, do this already. Downloading HTML is a thing. I just meant that since I can already do this, it would be nice if I could both do this and have it integrate seamlessly with my browser for navigating links and host those files for other people while on WiFi I was at it)
Save as HTML is often completely broken. Especially when javascript injects <script> tags to load even more javascript. You're better off by using archive.org's wayback machine.