In the video that is at the beginning of Assassin's Creed, Altair has a crossbow that he uses to shoot the guards. Does anyone know why this feature wasn't added to the game?

The crossbow wasn't a very common weapon during the 3rd Crusade, seen mostly during sieges, and never outside of military use.

So to see someone carrying a crossbow who isn't wearing a military uniform would attract way too much attention, especially for someone who is supposed to be stealthy like Altair.

And plus it wasn't mentioned in the lista of weapons tht was mentioned.