Why I run

1. Improved cardiovascular health.
2. Improved quality of life in my later years.  Most studies show that you don't improve life span much by exercising, but your quality of life improves dramatically in terms of mobility.
3. Decreased lower back pain.  I used to be afraid of breaking into even a jog because of the very real possibility of throwing my back out with the sudden movement, particularly in the Fall when temperatures got cooler.  Every year I could almost count on my back acting up. I think I have arthritis in my back and the cooler season does trigger these inflammation type reactions, but they are generally less intense.  Breaking into a sudden jog no longer concerns me.
4. Improved cognitive function.  Numerous studies have demonstrated improved cognitive function in response to exercise.  Just go to Pubmed and do a search.
5. Weight loss.  I don't really worry too much about weight loss, however...at one point during my commuting years I hit 170 pounds.  My doctor told me to lose some weight.  Fortunately about the same time I got my tenure position at the local college.  I hit the gym more regularly, and at my son's suggestion added cardio to my work out - elliptical machine.  I was able to bring my weight down to ~155-158.  My doctors wanted me to lose another 5, but I felt good, my muscle mass had improved, and I figured the 5 pounds was muscle mass.  Running knocked off those 5 pounds.  Adding interval training, the long run, and 60+ miles per week have brought my weight down to 134-138 pounds!  Muscle mass is still good - I do resistance training.
6. Improved energy.  
7. Improved mood.  Many studies have also shown that exercise helps with depression.  I don't struggle with this a lot, but I have noticed a reduction in my down moments.
8. It gets me outside.  As a gaming geek I spent too much of my free time inside looking at a computer screen, or small miniatures at a painting desk or gaming table.
9. It gives me a sense of accomplishment.  I can set goals and strive for them.
10. Running is epic. Changes are slow. The evolution of running span years, and I love that.  It isn't easy and not everyone is willing to do it.
11. Improved social life.  I've met people running.  People who don't know me walk up to me to ask about my running, or that t-shirt I was wearing while I was running.  At the only local running event, somebody who recognized me from coaching my son's soccer team years ago came up to talk to me.
12. A reason to travel.  International Marathons and Half-Marathons.
    
13. So I can eat more ice cream.
14. To prepare for the zombie apocalypse.  I just need to run faster than the zombies and the slowest non-zombie.
15. So I can buy running shoes.  Seriously, this list could have begun an ended with this one item.  Most runners run more weekly miles to improve speed and endurance.  I run more miles so that I can buy new running shoes more often..