You're free to run your own app store, like Amazon fire devices, and not subscribe to GMS. Why shouldn't Google get something in return for enabling phone makers with an OS and app store? They're a for profit company after all
It's obvious that Android has enabled and continues to enable an ecosystem of hardware companies to thrive. These companies have tried repeatedly to build their own software, but with NO commercial success. Imagine a world with an Apple like Android, Google owning the software, closed sourced, walled, yada yada ... That's still a possibility if the ludicrous EU actions on Android don't stop. Google makes about 1/10th the revenue and 1/100th the profit off Android as Apple makes off the iOS product lines.
Android's ecosystem gets a LOT more out of Google than Google gets out of Android
EDIT: Samsung, LG, Huawei, ... they're even relevant in phones because of Google. I doubt it's the other way around. Samsung is SO scared of Google cutting it off that it tries repeatedly with alternate OS-es --> everything from Tizen to windows phones. Nothing sticks
Google doesn't need to make money off hardware or software, it's an ad company. Yeah sure they'll just go and remove themselves from mobile ads market because laughable penalties EU apply on them.
If the EU's fines are laughable, I think the status quo will persist. But if Google is beholden to Apple & phone makers who use the very OS it provides & builds, cutting others off and owning the hardware isn't far fetched. Why do you think HTC was acquired?