Many people don't know how to cut and paste via the keyboard. The vast majority aren't even aware of Alt+Space. The only reason I use Alt+Space is to recover windows from off-screen areas.
I'm blind and alt+space is sometimes the best way to access select/copy/paste on the terminal. some other apps that have terrible a11y experience as well, but usually I use it there to closethe app asap.
Is the terminal you're referring to within, outside, or both within and outside a windowing system? How does it work? I'm not able to find an instance where alt+space does anything related to select/copy/paste.