If apps start charging money, there would be a significant drop in the # of average user installs. Then the app would only make money off of privacy focused users, which is comparatively small.
Because they don't know.
Like every industry, there are practices involved to which the layman is oblivious. It is important to remind ourselves that the reason the majority of users aren't vocalizing their concerns with these unsavory practices isn't because they don't care but because they don't know.
Regardless of which SDK features they use the SDK calls out to Facebook with the device's fingerprint and a persistent UUID every time the app is launched or brought back into foreground.
A lot of software these days don't offer a way for casual users (read: not enterprise/small business) to pay for it. It's "free" or nothing.
And paid software (such as Spotify) still does shady stuff like reporting to Facebook that I'm a user of their app and the schedule on which I use it.
