Asking people to do things without a threat or weapon to coerce them with often doesn't work either.

Just because something doesn't work well when done right, doesn't mean it should be done wrong. There are ways to gather data necessary to inform product decisions without surveillance, or turning your users into non-consenting test subjects.

(EDIT: Nevertheless, I'm very happy about the values they describe and that they chose to store the data locally. It makes me trust the authors that much more, and conversely, if it wasn't local, I wouldn't even consider using it.)