Is it? I'm musically stupid, so the fact that guitar is hard for me doesn't mean much. But isn't it truer and more relevant that guitar is a popular instrument for amateur and casual players, because a) it has a big role in popular music, and b) it's accessible, in the sense that guitars can be cheap and they don't require a lot of space?

There are plenty of relatively easy guitar pieces (especially if you're satisfied with using the instrument as an accompaniment to singing, or playing single-note melodies as part of a band), but that's obviously true of the piano too, and likewise both instruments have plenty of complex and technically demanding pieces. I'm genuinely interested in being corrected, but as far as I can tell the physical technique is at least as hard, and the possible musical complexity is no different. Is there any sense in which the guitar is actually 'easier' than the piano?