Because of the hardware requirements. So much phone hardware is closed source, binary blobs - at best.Why are you amazed? People want Linux! I'd actually love to have one myself.
If you are looking for alternatives to Android, there are a few:Can anybody build a replacement for the google phone os? Now's the time to get together and get it done!
Yeah, if you are on Android, it is not that easy to get rid of Google services, especially Google Play Services. You can try removing it by rooting the phone that is using software like KingoRoot. But rooting is not easy for most users. Sometimes it works but sometimes it is not.Google also locks down your phone and doesn't let you customize it (vendors do this too). A good example is a way that you cannot uninstall Chrome.
Even if you don't use Google products, Google still tracks you as long as you use the internet. The majority of websites on the web are using Google Analytics and Google Adsense, which means your visit to these websites will be tracked and logged by Google.They have too much control and way too many tracking aspects to their platform. I also think the people on here would be better at building a cleaner OS that would be easier for the tech-challenged older users.