Want more room for your seat on the plane? How about buying it from the person sitting next to you.
If the seats could have arm rests that move left and right from a middle neutral position by some increment it could allow people sitting in the seats next to each other to make more room for one vs. the other.
There’s plenty of times I’m sitting next to someone on a plane and think ‘wow, I’d give that person 10 bucks or buy him or her a beer if they’d let me move the arm rest over and get more room.
At the end of the flight the seats would all re position themselves back to the middle.