Can someone ask a trucker?

Why is it, that when there is a lane closed on the interstate, a truck will pull into the center of the highway to prevent people from driving to the merge point? Even when a sign says, "Use both lanes to merge point"? Is he upset because he picked the wrong lane? All he is doing is increasing the delay. I really want to know why truckers do this, but I don't know any, and when I pass the self-appointed emperor of the highway, he can't hear me cursing at him under my helmet.