There are compelling reasons to share data. Whether or not it's enough to compel you isn't really the point. Most companies that are harvesting data are using

There are compelling reasons to share data. Whether or not it's enough to compel you isn't really the point. Most companies that are harvesting data are using it to offer some sort of service to the users' benefit, on top of using it to advertise to them. Sometimes the benefit is just "it syncs across devices and I don't have to run my own server." Not everyone is technical enough to do that. And sometimes, things just see very straightforward, and not worth hiding. Different people have different levels of tolerance for things. For some people, period tracking is very much health information. Some may just find it very personal and view it as such and not use an app, or some may be trying to get pregnant, so it's explicitly health related but worth the risk... but for others, is just something you do, and it's not "health information," it's just trying to keep things predictable. Everything comes down to "if things change, what are the odds this could be used against me?" when it comes to privacy. Maybe talking about privacy online becomes a negative thing under a totalitarian government that wants to quash that kind of speech, and this conversation we're having right now is a terrible idea. Probably not, but just sharing your opinions on things (literally any topic) is private information that could used against you, if you construe it properly. But we consider that scenario unlikely, so we have the conversation and share our thoughts and express ourselves online. And a little bit of data about us is added to the pool.