For starters, air travel is frustrating enough these days. So it just makes things worse if you insist on fully reclining your seat back when the person behind is already squished. Or if you walk down the airplane aisle letting your carry-on bag smack into the faces of folks already seated.
And then there’s this: if you get really out of hand, say by getting into a fistfight with another passenger over the armrest, you may have to answer to a Federal air marshal – perhaps the one who recently set a new world marksmanship record for shooting the “Roundabout” in 8.08 seconds during the “Speed-On-Steel Championships.”
(From TSA site)