too close on the metro

Why is it that there are 100 or more empty seats on the metro and the biggest dude has to sit next to me on the metro?? I just don't understand it, WWWP? Don't people have some common courtesy when it comes to this issue? It's like when you go to a movie theater and there are empty seats through out the whole theater and the tallest guy/gal has to sit right in front of you? I stand at 5'4" and it's not easy to see the screen when someone sits in front of you in a theater, at a concert, at a sporting event, let alone a tall person in front of you.

life goes on :)