A lot of them don't know they're doing it. The tracking itself is embedded in dependencies of dependencies. SDKs you add for legitimate purposes. Along the way it's sent from platform to platform. Analytics, add targets, and eventually data brokers. Data brokers then sell it to other data brokers or the government.

If you're lucky, it's pseudo-anonymous. Of course it's actually not - aggregated location data is inherently not anonymous.

Should be obvious: lots of money in that. Corporations are amoral psychopaths.