The reason for that is that the technician gets paid what the book calls for regardless of how long the repair takes. If the book says the job takes 2 hours and it takes the technician 4 he only gets paid for 2 hours. If the book calls for 4 hours and he finishes in 2 hours, he gets paid for 4 hour.
They have to be fast if they want to earn a living. The slower technicians always leave to find a better occupation.
