Modern DSLR camera lenses are full blown embedded computers controlling mechanical actuators (focus motor, aperture blades, etc.) and communicating lens information to the camera's CPU (aberration corrections, vignetting corrections, etc.). The days of lenses just being collections of mechanical cams for moving glass elements back and forth disappeared a great many years ago.

Modern lenses are complex electronics now. They need to communicate with the camera about correction params, metadata, control algorithm for focusing and stabilization. Having a usbc port is a natural next step.

Lenses have energy budgets, responsiveness concerns and actuator/sensor pairings through embedded processing. Therefore they need firmware. Firmware goes out of date and has bugs and improvements. Having the ability to configure a lens beyond simply selecting firmware is an obvious second use of the required interface.