I just got home today from a trip down to the Gulf and it seemed like for every three or four trucks with a trailer on the interstates there was one without. It seemed unusual to me. Is that normal now and if it is why? Seems like lots of driving for no pay.

I believe they call it "dead heading". Happens when they don't have a load booked going the other direction, so they deliver the load they were paid to, and have to go home wether they booked another load headed that way or not.

I thought dead heading was an empty trailer. It seemed more frequent further south so I wonder if they do it less up north because of traction issues without a trailer on snow or ice.

You can deadhead with a empty trailer to.

Many drivers that are owner-operators take their rigs home if its gonna be a few days before the next load. So if you're near a trucking company, or multiple ones that uses owner-ops you'll see a lot of bobtails on the road

hauling an empty trailer isnt much better on the ice vs a bobtail. even worse for tanker drivers is a tank that didnt get completely empty and you got stuff sloshing around.

Dead heading is usually done with an empty trailer between the last drop and the next load.
But it does seem unusual to see that many bobtails. I spend a lot of time on the interstates and sure don't see that many.