Because if you don't pay your taxes, the government will insist that you go to prison.
The problem isn't really what google is doing, the problem is that were letting our existence as free citizens in a society depend on a piece of blessed hardware/software we must carry around with us everywhere we go.
We need to strongly resist having software/to become strongly codependant on hardware broadly speaking. But especially software/hardware that we can't control and which is sold by two american companies.
Quite a few banks in the UK now require an app, and that's a liability for me as who knows when they'll arbitrarily decide to lock me out of my account because I am not running stock google android.
The bank I'm with uses a hardware token which I can tolerate because, while it does require a codependence on hardware, at least the hardware is provided for free by the bank. I can also manage my account over the phone without the hardware.