I have been running since 1982 (not counting high school!!), averaging about 1000 miles per year.
I started running for my heart and my lungs (I have asthma, so my running helps me master its management). Then after not too long, I realized that the part of me that most needs to run is my head. Running relaxes me, and it is that effect which gets me out the door most mornings.
Yes, I run in the morning, usually at about 5:30 AM. The quietness of the day affords me the peaceful environment I most enjoy. Running at that hour doesn't intrude on any family time, and it doesn't allow those inevitable things in your life that keep you from going later in the day. I run alone, and while my performance would no doubt improve by running in a group, I love the peace of having those moments of the day all to myself.
I have run on five continents... Africa and Antarctica await. Running is a great way to learn a new place and see some fascinating sites. I have run in only two places where I was afraid: Singapore (afraid that I was going to run through a red light and get caned for it!), and Sao Paulo, where the area near my hotel was considered unsafe for tourists. My favorite runs are those longer routes in any place I am visiting.
I keep a diary of my runs, and have for over 20 years. I'm not certain that historical analysis or reflection is of value, but the recording of my route, distance, weather conditions, weight, and how I felt get me to think about what helps me run best.