I think the reason this happens is largely because the "common" (non developer, non technical, non engineer etc) user demographic, because of services like FaceBook, Insta, TikTok etc, don't see a reason to pay for software. Therefore, if a developer wants to make money (especially if they're a solo developer) they tend to sometimes walk the less-ethical side of software dev and hoard / share data do make their effort a bit more worthwhile in terms of generating revenue.
It's also troubling to me that large companies like apple want to make large scale "anonymized" health data collection common place and "normal". Citing "huge leaps in medical science" as a reason to start mass data reporting on their users.