Some in the cyberdeck community build these as mobile coding stations, for example a way to head to the park or a coffee shop to run emacs without any of the distractions of their regular machines. Some use them as mobile writing machines, like an old school wordprocessor (think Tandy WP1). There's another big portion of the cyberdeck community that's primarily in it for the aesthetics. Or a combination of all of the above. The hobby is kind of about personal computing in the personal, idiosyncratic sense of the word.
Great answer, thanks, I was wondering the same. I love the "switch" switches on this one, especially the one with a red fold-down safety.
There is no specific use (at least for me at the moment). It's just a prop I guess although it's fully functional. The whole thing for me was more the process of building it.
The aesthetics of a 1) mobile 2) rugged 3) cryptomachine straight out of cipherpunk universe.