From what I know, this is one of the things that make the car-dependency in the US a serious issue

I live in the capital of Norway, and damn near everything here is in walkable distance, and it's so great. If I go somewhere I either take the public transit and/or walk, which really does add up over time. I can end up walking for many hours each week, which doesn't feel burdensome or boring, and can effectively replace the treadmill. Then maybe take a few more brisk walks beside the river if I feel like it or something like that, which is nicer than in a gym.