well, if the forum causes the server high loads, it will go down more often and i'll have to buy a dedicated server, which will cost me more money.
But picture this: image someone starts a thread, and in the page there are 10 posts. each member has 3 images in their signatures. and the total size of images of each member is 250Kbs or 200Kbs. That's a 2/2.5Mb page load! That's horribly long for those who have slow internet connection, plus, the images are not all hosted at chocobo heaven, so any slower host, will cause the forum to be slower too!
I think everyone understands that this is for the best.
Edit: And I have already changed my signature.