Sadly this point gets lost, I just generally chalk it up to some people don't know what to say or don't want to mimic / parrot what others have said, but its like if they are gonna fave it, they could say why they like it.

Honestly I'm guilty of flicking through latest submissions and just favouriting, though often go back later to comment, though I know a lot get put off commenting on a pic if its more than a day old as well, assuming an artist won't want to be bothered on an old pic they drew.

so a bit of catch22 going on at times >__<