Can't you just see the mayhem at the airport.
All pax have vetted the crew and happily checked in. At the last minute Bloggs trips on the Jacob's ladder spraining his anke, so Fly With Us Airlines calles in two reserve pilots and advises the pax.
They all take to their iDevices and research F/O Mustaffa Abdallah, 5000 Hours on type but what about that name. And the other option is F/O Cissy Cadet, 250 hours just out of cadet school.
So all the pax withdraw from the flight, and are now arguing with the checkin staff that they must get on a flight with pilots that THEY approve of because they have a very IMPORTANT meeting to attend.
Sheesh!