Earlier quoted context omitted.
All major browsers implement a HSTS preload list[1] to get around the first connection problem. Manually deleting the HSTS pin for a site is quite involved and not something I'd expect most users to do. [1]: https://hstspreload.org/
Preload lists are not a realistic solution (you can't preload the whole internet) and a sufficiently complicated site will be subverted due to 3rd party dependencies. And does uninstalling a browser not clear the hsts cache?
I'm not certain if uninstalling a browser clears the cache (do uninstalled browsers retain their profiles?), but preloaded sites would not be affected - they're included in the browser binary. Either way, let's not act like there's a massive hole in HSTS because there's a possibility that users might go as far as reinstalling their browser to visit a not-preloaded HSTS-enabled site that's being targeted.