The regulation calls out 19 vehicle functions which must have physical controls inside the vehicle, with additional requirements about size and usability of the buttons.
Those functions include:
Turn signals
Hazard lights
Horn
PRND gear shifter
Driver assist function, if present
Windshield wipers
Windshield defroster
Power windows
Emergency call system
Power off switch for EVs
My work van has an emergency call system and it malfunctioned and dials it all the time, especially in low service areas. This causes it to constantly dial the SOS number and the only way to stop it is push a tiny hang up button on the infotainment system. The hands free controls for calls don’t work with the SOS system. It is incredibly annoying, distracting, and dangerous. It has been back to the dealer 3 times to fix it and has yet to be fixed for good.
So a physical button for this system is very important.