The SPI and I2C protocols have their particular corners in the IoT and embedded spaces. Odds are if a sensor is not equipped with a data radio, that sensor will most likely communicate with a host device using the SPI or I2C protocol. If the Raspberry Pi 4B is to operate in IoT and embedded space, it must be able to obtain and exchange data with devices using SPI or I2C. In fact, the Raspberry Pi 4B is fully capable of utilizing the SPI and I2C protocols. It is up to us, the C programmers, to put the Pi to work as an SPI-capable IoT device via its native GPIO subsystem.