They're here to moderate the forums and keep them clean. The rules are so people know what they can't and won't get away w/. Other than that though, there's no reason you shouldn't be punished for doin' somethin' you should know better than to do. Advertisin' on this site is an attack against it, of sorts; the moderators are here to get rid of that and keep this place clear of such things, whether they're against any written rules or not. Don't forget; it's their forum, you're jus' a guest in it.

For example, you're visitin' someone's house. It's not against any law to open the fridge and start eatin' it all, but damn you're gunna get a boot up your arse if the owner catches you.

They can uphold any rule they like and the best you can do is deal w/ it, or you can leave. Don't forget, you agree to the ToS by joinin' the site and usin' it.