Simply, put I think from this quote.
"Chess is life" – Bobby Fischer
I play chess and Billiards. I see similarities in the games, and neither sport is physically demanding. However, people's attitudes are completely different towards the two.
I play chess because I believe it excercises my mind, and it allows me to procrastinate non-stop. (Thanks again Erik!) I also play a lot with friends, but my initial goal was to become better then my Dad. He won't play me anymore :( So now I'm here playing chess.
Many people ask this question, and derive a definition that only excentric and boring people play this game. On the contrary i think that this game enables you to make new friends, develop new aspects of thinking and of course have fun.