I have the choice to buy a phone without bloatware and I did. I don't know why others don't do the same and then blame the OS maker for allowing their open software to be open.

These policies also allow for cheaper phones to get into the hands of the less affluent. Not everyone can afford the new iPhone, and they would rather have a phone with a bit more bloatware if it cuts the cost of the phone down to something they can reasonably afford. I would consider that a noble endeavor on the part of Google. Instead of saying, "FUCK YOU CARRIERS/OEMS, YOU DO AS WE SAY!", it offered them a means of providing cheaper phones without decimating their bottom line. They can choose to strip out all the bloat and price it high or they can bloat it up and price it low, making up the cost from the recurring fees/ad rev those apps can generate.

The thing is, I have a choice as to what experience I want.

There is Android, which is a complete open source operating system tailored for touchscreen devices. It is completely open source and in principle has no dependencies on any piece of propietary software to function. Android is not usually distributed with just its open source components, however.

There is Google Play Services. This a propietary set of applications and system services that interact with Google's cloud services. Since Google's cloud services are popular - most significantly the Google Play Store for Android apps - these services almost always come bundled with devices on the market. Android and Google Play Services together are also often called "Android" (even by Google itself) which is the cause of the confusion. There is a clear difference between the two, however.

Then there are further customizations in themeing, user interface components and applications made by vendors and carriers.

The problem of bloatware is that Google has only felt responsibility for Google Play Services; the other software on the system, including Android, was the responsibility of the carriers and the vendors. Android is developed by Google as an open source and popular foundation from which to provide its services - either from Android's web capabilities or from its bundled applications.