Comfort and Convenience
Height, leg length and preferred posture differ from person to person, so a seating position one driver settles into naturally can feel cramped or too distant for another. A shared car usually means readjusting at each changeover.
Safety and Driver Assistance
Finding the lights, wipers and hazard switch while still parked means less searching later, when a sudden shower or an unlit turning leaves little spare attention. Borrowed and hired cars make that minute worth spending.
Multimedia and Connectivity
A phone running flat partway through a journey is a common annoyance, so charging is a separate need from audio. Where calls can be answered through the car, the phone itself stays out of your hands.