I can't speak for others. But, personally, the
principal reason is,
they typically look like crap when displaying at anything but their
native resolution and are too stupid to be told to fix it.
Please, use a M1721A or M1921A...You'll be VERY surprised.
Do you want me to take some photos using classic computers (I have here ZX81, MSX,
Amiga that I can photograph today) and show them up on a page?