Look up the the Battle of Crécy which explains how rain causes crossbows strings to absorb moisture.
The problem with realism is that Crossbow suffers from all possible IRL penalties -
crossbow is the only weapon that can malfunction - you get hit and your bolt gets stuck and bye bye you can't use your crossbow anymore. At the same time, it does not have realistic advantages (it should not cost any wpf at all to be precise, and should have much longer range).
Realism? Sure, let's see how it would look like. How about someones sword shattering? How about that? How would some 2H guy feel if he hits someone 3x and upon manual block his sword breaks or his axe gets cut in two after attempting to manual block a bardiche?
How about I run over you with a Charger and you instantly die because I trampled your spine?
How about your arrows do zero damage to me because of my good armor?
How about you breaking neck when falling off the horse?
How about people who run up the hill get fatigued by the time they reach me, which lowers their combat efficiency?
How about my crossbow having real actual realistic range?
I'm addressing serious balance issue here. Not making historical simulation which this game is not.