Comfort and Convenience
Preferred cabin temperature varies from person to person, and passengers often want something different from the driver. Agreeing on a setting early tends to save constant small adjustments during a shared trip.
Safety and Driver Assistance
Setting the seat, mirrors and steering position while still parked keeps those adjustments out of the driving task, which is worth doing in any car that is new, borrowed or shared.
Multimedia and Connectivity
Hands-free calling depends on the car recognising the phone, so any pairing is best done while stationary. Music playback and charging are handled separately and may rely on different connections.