[Jallal]

Same for me (actually, most of the people I know are focused on running, but I guess it could be applied to nearly all sports).

The closer I get to my forties, the more important it is to take care of my body. Basically, you just realize that your body is not what it used to be, and you have either the choice to do something to stay/get back in shape (more sports, a better diet), or let it go (which is, unfortunately, the first step to health complications).

There is also a strong bias regarding to whom you hang with then. Being "seriously" involved in any sport means that you are going to dedicate a significant part of your free time to training, and therefore, will spent much more time with your fellow sportsmates than "regular" friends.