For me, it's not so much the quantity of miles driven as the quality of time I spend in the car. Commuting to work was very stressful - traffic jams, aggressive drivers, bad weather, arriving late due to unexpected delays, etc. I used to leave home well before 6am to avoid the worst of rush hour. In the winter, I often drove to and from work in the dark.
Now I can avoid rush hour and if I do get caught up in traffic, no big deal. So what if I'm a little late arriving at Home Depot?