Alcohol is an intoxicant, and there are a variety of risks of society as well as the individual, thats why it is not allowed. Pork is not allowed for many reasons, most of them considering whether it is sanitary or not. This is not the promotion of just good morals, but it is rooted in Islam, which is why they are not allowed.
Shisha (or hookah for english speakers and some other regions) is just tobacco with fruit flavor and molasses. There is no specfic law against smoking it in Islam, thats why it is allowed.
(though there is some debate based on hadith, or, whether it harms you, can you still smoke tobacco)
I think it is not good for your health if it is done too often, but once in a while, as long as it doesn't harm you and it is not forbidden in Islam for other safety or societal reasons... I don't see why it promotes bad morals. Do you?
Plus, just as a side note, its not really allowed in Riyaddh all year round (but maybe in other areas of saudi like Jeddah it is...)
