All of this is also true for modern CPUs, yet I don't need a driver to talk to CPUs because the ISA serves as the abstracted and standardized programming interf

All of this is also true for modern CPUs, yet I don't need a driver to talk to CPUs because the ISA serves as the abstracted and standardized programming interface to the underlying CPU hardware. If GPU vendors wouldn't be so keen about protecting their "IP", GPUs could have gone that same path.