An additional problem with xbows is the frequent rain which makes them work at 75% efficiency or so I've been told by mr. cmp (I've shot a 10 IF fatass-->that's 85 hp in transitional armour four times with my "95" piercing damage and guess what, he lived, came up the hill and slaughtered my buddies
.)
The 873 upkeep just isn't worth paying for a gimped-by-rain weapon, so a dedicated crossbowman is forced to either use it anyways in cloth armour or take his chances with just a melee weapon.
During sunshine, the damage is okay. You can usually kill archers with 1-shot at close to mid range, long range it often takes two shots (that's with a masterwork siege crossbow btw) but the upkeep still forces you to cry sometimes if you can't get that precious x3 or more.
You also don't see many dedicated crossbowmen because they can't just take an xbow with 3 bags of bolts and run away from any sight of nearby melee and kite them because they have to reload and that can't work as good as archery.