You are right that SPI is a standard, although like RS232 it only exists in hardware and data layers, while USB is up to application layer. You argument in thi

You are right that SPI is a standard, although like RS232 it only exists in hardware and data layers, while USB is up to application layer. You argument in this case is very similar to defending use of custom TCP protocol for web browsing. While TCP is standard, there is nothing standard about it to browse the web, we have HTTP for that