Why are my Sims wearing paperbags on their heads?

I think the paperbag thing came with the Eco pack but since I think it's ridiculous I have never used it but all of a sudden I'm seeing all kinds of sims walking around with these foolish bags on their heads for no reason. I can only guess it is some kind of unexpected reaction to some mod I am playing with in my game because I can't see how there is any good from this in actual gameplay.