Because the risk isn't worth the money saved, and I imagine if you got deliverability statistics on those e-mails you'd find that many of them don't make it to

Because the risk isn't worth the money saved, and I imagine if you got deliverability statistics on those e-mails you'd find that many of them don't make it to the recipient. Many web-based companies would effectively be out of business if their web server was listed on a few major blacklists.