Why do trucks line up beside each other at stop lights?

When you're pulling up to a stop light and there's an empty lane, do you pull into the empty lane or do you get behind the *** in front of you on his cell phone?

Personally, I like to drag race, so I pull into the empty lane in case someone wants to race me.

It still makes me mad when 2 18 wheelers do this though, I mean are they going to race? Really? Or are they just going to keep me from getting where I'm going.