[ust]

That well may be (regarding the power management), but while SPI as standard is old, the use of SPI is not standard. I've implemented quite a few SPIs (mostly FPGA) to interface with various commercial devices and virtually all of them had a different protocol, i.e. 8bit vs 7bit words, different bits to denote write or read, etc. Some of them didn't even use SS signal. I wouldn't really called them standard, and I say that with regret. More hardware could be used in a more standard manner.