The Only Question is Why?

I took the Metro into work today and because I start at the beginning of the line, it is generally easy for me to find a seat. This is helpful because of my long legs, I can only comfortably sit in certain seats. This morning, like most mornings, I found a seat that was comfortable, so I sat down and started reading the newspaper. By the time the train was at the third station on the line, the metro car that I was in was starting to fill up. It was at that point, the most perplexing thing happened. A man, who could easily be viewed as a toothpick, sat down in the middle of two seats. For those of you that are not familiar with DC's Metro system, the seats are paired in groupings of two. Rather than New York's subway style of lining the walls with seats, Washington's style is more reminiscent of train or standard bus seating. Then he took his briefcase, which again was as thick as he was fat and put that next to him. Just seeing this perplexed me, but what am I to do? There were still a few extra seats, so it was not that he was preventing anyone from sitting down. That is, until we got to the next train station and the Metro car that I was in was standing room only. Still this guy refused to move. People would just stare, and one even said "excuse me" three times, but the guy just sat there, with his legs sprawled open preventing anyone from sitting on their side of him. I am guessing that if the chairs were hard plastic and not cushioned then maybe it wouldn't be as comfortable, but nonetheless, he didn't seem to mind. When I saw an elderly lady standing next to him, I offered her my seat so she could sit down. While I would gladly make such a gesture, it would have been unneeded if the guy decided to sit in one seat. So the only thing I was left to do the rest of the way to work was wonder, "Why?" Does anybody have a similar experience or have an idea of what I should have done?