Even if Google is using statistical sampling, it's still something they'd want to collect directly through the app, not via a third-party.
As for paying individuals for their data, Google does that too. https://play.google.com/store/apps/details?id=com.google.and.... But if your argument is "They should be paying everyone they collect passive samples from during use of their products," that's an argument over price-point, not over whether the collection itself is right.
The rightness question seems to me to look a lot more like "If you can collect data from a billion users without doing any harm to the users, and that data is going to be more useful than a statistical subset of that data, why should you not collect it?"
In this particular case (speech recognition), one harm done to the users is tying the product to the Internet, and thus requiring what should be closed-loop tasks to go through vendor's servers.
My impression is that the main driver behind cloud-first voice processing is business, not technology.
For a company that supposedly is employing the best minds in statistics, the inability to effectively use statistical samples is, uhm, intriguing.