the problem become , the honesty in all of this. Those people dont pretend they want nice personal graphs. They pretend, and believe (I guess) , it help them exercize and lose weight. The industry of tracker-maker, is more than happy to keep the illusion going. It's the new face of the very prevalent weight-loss scam. I follow the r/loseit sub. Every other comment/post, is about how some fucking tracker helped them. it didnt ! Those guys lose weight despite the trackers... As science just proved it here.
There is a Fitbit tracked activity component in two of the research studies I work on. We were worried about this confounding our results but it seems like people only really change their behavior for a little over a month after they start wearing a Fitbit. After that counts and heart rates tend to normalize and approach their 'real' activity level.