Why is the most popular computer os closed source while the most popular mobile os is open source?
I don't understand why Google didn't just made Android closed source. They would've made custom roms impossible and therefore more able to control and spy on it's users. Why did Google made Android open source, while Microsoft's Windows is still closed source to this day?
Android is effectively closed source anyways. If you use this OS without Google Media Services, you will be effectively locked out of almost any app, system, service unless it works in a browser.
If your use case revolves around a limited amount of apps and features, I can see how that would work. If you travel the world, experiment with new services etc. you might end up that the only way to obtain the required service or information is an app, which mandates GMS, which goes for an absurd amount of programs, and if you don't have that, that's it. No access to the service or information in the middle of the road and sometimes nowhere. I used a degoogled system. It is everything, but certainly not everyday usable. As a secondary phone perfectly fine, but not as a primary.
Of course you could start a debate with the developers of why their public or event service relies on Google, but good luck until that is implemented when you are locked out right now.
I can tell you why app developers are using Google services.
They provide a lot of important features, which are hard to implement otherwise.
Unlike others, they provide these features for free or super cheap.
Everything is well documented and they produce tons of educational video content. For free.
Most app devs use them, so it is easier to find support, code examples, etc.
All this leads to a situation where using alternatives is just too expensive and will increase your development time noticeably (and that will be expensive too). Large companies can bite the bullet and just write off the losses, simply because they don't like Google or whatever. But for a smaller developer that's a death sentence. And if you're creating a free app - just forget it.