Internet companies outside of the ad space also track you because they can use it to analyze and increase sales, much like grocery stores. They use it to inform product decisions by answering questions such as: Which features are our users using the most? Which features are the most profitable users using the most? How do we get more people to the end of the sales funnel? etc.

Are you ok with this kind of tracking? Genuinely asking... Personally I see it as "less bad" than straight up selling my data to another company, but I would still prefer companies didn't automatically track me at all, and instead relied on interviews with real users. Or at least make the tracking opt-in, Nielsen style.