I don't really object to them, but relevant? How often do they come up? (The only thing I can think of is chasing ambushers who are fleeing after attacking the PCs in their inn room. Although there don't seem to be any rules that penalise sleeping in armour.)
They would come up every time the players post a watch at night and one of the guys says My character sleeps in his chain mail. oh no, it's totally realistic. I've done it myself a dozen times..."
I think it would come up literally every night of adventuring.