As someone pointed out already, the reel was invented in early Medieval times, so it fits in just fine.
And as about a thousand or so people pointed out when the no-crossbows thing was first announced: they never made sense as a weapon for an individual traveler in the first place. They take forever to reload, and they're much heavier than a bow. They were used by large groups of infantry.
Yup, this is correct. While I want it back in the games for the pure nostalgy and for the hell of it, it makes little sense. The crossbow was designed for anyone to use easely, as bows required expertise and much training.
They were given to large troops of militia soldiers mostly, who then could easely use a ranged weapon with minimum training. If they had a wall or something to cover them up, the reload time had little to say.
But I still want them back.