The quick boarding and exiting times are important not because they provide a customer service advantage through convenience, but because they reduce the amount

The quick boarding and exiting times are important not because they provide a customer service advantage through convenience, but because they reduce the amount of time the aircraft spend on the ground. Time spent on the ground is basically waste from the perspective of the airline, and this is especially critical for short-haul routes where these delays add up to a significant portion of the aircraft's day. If the aircraft is flying 1 hour trips, and you can reduce turn time from 20 mins to 10, that means that the whole trip is reduced from 1hr20min to 1hr10min, which works out to a 12.5% shorter trip time for the given route. This means you can either transport 12.5% more people on this route with a given number of aircraft, service 12.5% more equivalent routes with these aircraft, or reduce your fleet size (and marginal costs) by 12.5%.