>The same way you know you can run any command with `--help`.

Not really though. Some command in the distant past once told me that I need to type /? to use the correct parameters. And then another one told me that /? is invalid, I need to type --help for help. And thus, I was aware. Contrast this with youtube, which I use for 10+ years now, where I have 500+ videos sorted into playlists, and I even know some shortcuts - discovered mostly by accident - and never once saw the "?" help page, until I read this hacker news thread.

Anecdote, I know.

In fact quite a lot of commands also respond to -?, which is my guess for what inspired this.

Either way, even an extremely imperfectly honoured convention is better than no convention at all.

At least there's a man page for those, there's no man page for crappy websites.