That way we know that something got through, and don't end up driving the moderators nuts with repeated postings. Because sometimes it seems like the words have dissappeared into the ether. Also it couldn't hurt for some of us forgetful type folk. :shrug:
And maybe a list of denied posts couldn't hurt either. Because if there's no email, it's hard to learn if you don't know what was wrong. I'm sure this would be useful too.