It vexes me that almost no one uses the real minus sign. But you also can't blame them since it's never been made readily-available. So you really have to be pedantic and spend time going to get it if you want to use it.
Most people aren't even aware there's a "real" (or rather, fake) minus sign. I didn't know until reading this thread. The hyphen is right next to the +/= key, so it's not unreasonable at all to think the _/- key is minus.
Yeah I had no idea either, but I'm sorry to say it's going in the same bucket as using a real em-dash vs a double hypen--if it's not on my keyboard it's not gonna happen.
Mac OS has option+- for en dash and option+shift+- for em dash. I used to add similar bindings on Windows via AutoHotkey (which is an amazing app all around...)
There's also option+space for and other goodies. I recently added option+x for "checkmark x" and option+v for "checkmark v" since I like dropping those around more often than I should...
This. Em dashes are—as punctuation goes—downright sexy, so I committed shift+opt+- to muscle memory long ago. And it's arguably less work than a bucked-toothed double hyphen.
Btw, if you haven't already, check out Karabiner on macOS for AutoHotkey-esque functionality.