The cost of cables and receptacles is quite a bit lower for Micro USB Type-B connectors and these microcontroller products have tens-of-cents (or maybe even les

The cost of cables and receptacles is quite a bit lower for Micro USB Type-B connectors and these microcontroller products have tens-of-cents (or maybe even less) in price sensitivity. The RPI4 has far less sensitivity and USB OTG, so it uses USB Type-C.