I think square or not may be a generation factor. Many younger photographers today have not shot a film camera at all, they don't know what they miss. If you're used to a rectangular format, like all digital cameras today are, I guess it's harder to see the advantages of square.
However, I might be wrong. On the web square presentation of portfolios has gained huge popularity, so younger photographers are surely familiar with the format although their camera's sensor is not square. It's a very practical format for showing a collection of images.
Personally I prefer the 4:3 format. I do sometimes crop to square, but more often keep it at 4:3, vertical compositions often get cropped to 5:4 though. But then I shoot landscapes with a tech cam from a tripod, not hand-held portrait photography. Not having to rotate the camera does seem like an advantage, I find the 3:2 format on my DSLR to be a bit awkward, sure there's a grip for shooting in portrait position but then I don't like the placement of the viewfinder.