The pickup time follows the aircraft, not the schedule you booked weeks ago.
The chauffeur waits while you clear baggage and customs.
The chauffeur handles the bags from the carousel to the boot.
For a single traveller with one bag and no deadline, a taxi or rideshare is cheaper, and we would say so. A chauffeured transfer is worth the difference when the arrival matters: a client you are hosting, a family with four suitcases, an early flight where a missed pickup is not an option, or a group that would otherwise need two vehicles.
The fixed quote is the other reason. There is no meter, no surge and no surcharge for a delayed landing, so the price you approve is the price you pay.