Comfort and Convenience
On a night run to the station, some people prefer a dim cabin, while others want brighter light to sort tickets, because those tasks need different brightness.
Safety and Driver Assistance
A quiet driveway is a useful place to find the horn and the hazard switch, because those controls are easier to learn when nothing else is competing for attention.
Multimedia and Connectivity
A passenger on a shared commute may want a playlist in the cabin. If audio playback is available, they can share it; if not, headphones are the fallback.