I have always enjoyed walking. Way back when I was in my 20's, it was because I did not have a vehicle, but I eventually bought a car. I lived downtown and worked downtown, so continued to walk. And I still like to walk.
First, I think its the best exercise, you don't need any special equipment, you don't need other people, you can just walk out your door and go. Oh, and it helps to wear off the beer I drink and the chocolate I eat!
Second, I find walking alone very meditative. I prefer to walk with no headphones or cell phone, and I prefer to walk by the river and get a little taste of nature in the city. Listening to the sound of the river, the birds, and the wind....
Third, I find this time great for creative ideas. Ideas pop into your head when you are relaxed.
I love to walk. I do not love to bike. I do bike once and a while but not as enjoyable. I miss the connection with nature. So when I go for a bike ride it's nice to just sit by the river and sketch. Always have a sketchbook!