Most of them are. :) Except for Huawei, I haven't seen an Android user not using Google Play Services. There is probably statistically-insignificant number of users just having F-Droid on a LineageOS who do not use Play Store, Push services or don't consume their ads. So most Android users are indirectly also Google users.
I'd wager that's untrue. Anyone who buys an app, or in app purchase, is directly a Google customer.
I'd also argue that even if someone uses Play Store services, but doesn't pay a penny, they're still a "customer" in a looser sense of the word. They're engaging in the market-place, likely using free apps subsidized by advertising. Even if you want to argue that they're the product instead of the client (and I'd be inclined to agree), they're still revenue-generating users.