I don't necessarily agree with you here. You could easily argue the limitations of, say, solo guitar, solo piano, or any given monophonic/limited-polyphonic synthesizer are equally restricting. Or solo clarinet, string quartet, etc. An ENORMOUS part of the popularity of chiptunes is the nostalgia factor and cultural/social element. There are tons of primitive synthesizers out there but the chiptune culture only really started to become a less-than-niche 'thing' around the time when anything retro or nerdy was becoming popular.
Please note I'm not saying anything about whether it's a "good" or "bad" style of production, I love chiptunes and have done some very poor attempts at them myself. I'm just talking about the popularity of them vs. the popularity of any arbitrarily picked production style or set of instruments.
Fair enough, I'll roll with most of that, although my comments were aimed more at modern electronic rather than solo acoustic instruments. My recent interest in writing chiptunes actually kind of came from a frustration with my own lead and melody writing, so it started as exercises with the limited instrumentation to FORCE catchy and memorable melodies out (which I strongly recommend if anyone is feeling the same way).
But I've been listening to chiptunes before I even knew there was a culture built around it (I'm so hip, right? Fucking LOVE Alberto Gonzalez's Gameboy work), looking up youtube clips of music from my favorite Gameboy games etc., and it was pretty easy to let myself be absorbed by the sound and turn it into a way of writing that I ultimately love. The process and the end product are both way, way too much fun