THERE iS A VIRAL COMPONENT AND AN ENVIRONMENTAL ONE (KNOWN CARCINOGEN CHEMICALS). I saw A DOCUMENTARY ON THIS. AND JUST CUZ SOMEBODY WAS LIVING CLEANLY IN YOUR EYES, DOESN'T MEAN THEY WERE NOT INDULGING IN SECRET BEHAVIOR THAT WAS KNOWN TO BE A RISK FACTOR FOR DEVELOPING CANCER.
THERE ARE REASONS FOR WHY THINGS HAPPEN.
Believe it or not, lobster and crabs are crustaceans and are a part of the arthropod family, which include caterpillars, cockroaches, and spiders!