Comfort and Convenience
Preferred cabin temperature varies widely, and passengers often want something different from the driver. Clothing, how long someone has been sitting still and airflow direction all change what feels comfortable.
Safety and Driver Assistance
A few minutes before setting off is the easy time to adjust mirrors and locate the hazard switch. Doing this while stationary means the first use is not also the first search.
Multimedia and Connectivity
Music and navigation prompts often compete for the same speakers, so a volume set for one can suit the other poorly. If a phone connects wirelessly, charging still needs a cable or pad.