They actually track your app usage and sell your data to third party companies. For example, right now Overwolf is selling data that is being used by NewZoo, which is a market research firm tracking PC video game usage.
You can see here in their help article:
The PC games data available within the Newzoo platform covers a variety of metrics and insights into the engagement of PC players and the performance of games.
The core PC game metrics are obtained through our partnership with Overwolf. Overwolf is a tech company based in Tel Aviv, Israel. They developed an overlay software that allows gamers to install apps that can be used in-game. They have 300+ specific apps for specific games. The Overwolf data sample best represents the male core PC gamer aged 15 to 35.
Source here: http://help.platform.newzoo.com/en/articles/4345617-pc-engagement-data-methodology#:~:text=The%20PC%20games%20data%20available%20within%20the%20Newzoo,a%20tech%20company%20based%20in%20Tel%20Aviv%2C%20Israel.