Seriously!
There is something that breaks in your brain.
The delight you feel when you see those little numbers go up when you're really active, immediately turns into a drug-like dependency to keep racking up those numbers.... that's why TV shows like Black Mirror are so scary, it's so close to what could happen.

I use mine to track my runs since I'm not using Strava... but I think for most people, if it gets them out and walking or running to satisfy their number-raising OCD then more power to them. Ingress and Pogo are amazing apps for this exact reason, Ingress especially...

Hahahaha, that last sentence is amazing!