I do have a car, but I walk as often as I can for the exercise, and to save gas/lower emissions. If the weather is shite or what I’m getting is too heavy or awkward (mega sale on canned goods or watermelon or toilet paper for example), then I’ll drive.
It also encourages me to go more often in small trips, which means fresh fruit and vegetables, and the freedom to choose what I want to eat on a whim rather than planning ahead a week or more at a time.