This is up to you where you want to walk. It is true that lots of people cannot stay outside all the time. So, they may be missing their walking session for a while. A treadmill is a great alternative for them to complete their walking or running session.
A treadmill comes with lots of features that make you feel outside walking. It has a pace and inclines system that can be set. If you want to get a very nice workout at home, then a treadmill is the best option for you.