I figured they’d be juggling a lot of mails
Yeah, but organized into as many threads as there are issues/PRs, so it’s exactly as daunting as the same list as viewed on GitHub/project/issues (because it is exactly the same content).
and I guess it is possible for some people to stay on top of that
It’s the crux of being a maintainer, it’s your job “to stay on top of that”, with, on larger projects, ad-hoc tooling and automation being the only way. Email is infinitely more flexible than the one-size-fits-all take by GitHub on that.
I came to bitwarden because we needed to share passwords with my SO and the way those replicate seamlessly on all our devices (desktop, laptop, iOS, Android) is a no brainer. Since bitwarden/vaultwarden is full self-hostable and open-source, I don’t see why I would pass on its convenience.