[quote=@gcold]
There were two types of crossbows in Morrowind, Steel and Dwarven. The Dwarven variant is not common at all, so it's out of the question. Steel Xbows, on the other hand, is only mass-produced by professional organizations like the Imperial Legion. Remember the Legion were much more powerful in the 3rd era than the 4th, which translates to less crossbows produced today. Although they take less training to shoot, they make for it with more training to maintain. A crossbow is mechanically complex relative to the standard bow. Not to mention, building bolts require a different and less known process than arrows. 
[/quote]

You're right about the crossbows, though I recall nearly every weapon vendors having one of the steel ones. I just wanted to voice my thought on the matter. After all, Bethesda is known to bend game lore to fit engine limitations.