is walking long distances for no reason strange?

Not really, if you can manage it properly. Something inside needs to tell you "it's time to start heading back home" approximately half way through the walk. But if you suddenly realize you don't want to walk anymore and you're miles from home, then it's a problem.

If it is then I'm very strange!  I do all my best thinking when going for really long walks for "no reason."  In fact, I'm currently browsing the net for a new pair of shoes as I've just killed another pair.  They don't make soles like they used to!

How about the reason to stay healthy. 

It's a healthy habit. Very good for the brain, heart and body. See interesting sights. And have time to think and process. It's also a popular habit. 

It's good for fitness when you prefer to be outside rather than in the gym. 

No, it’s not. I would walk long distances if I had the time.

No, it is a health form of exercise