Why is it that Android still can't be installed as regular OS?

Are there any technical or others reasons why Android is still a firmware and not an OS which can be just installed without a lot of hassle? Why there is no universal image which could detect appropriate drivers (kernel modules), partition NAND in some standard way and configure boot loader to boot updated OS version? What stops Google from making a real (less firmware-like) OS (an OS for small ARM, x86 etc. devices)?