Yes as has been said there are those out there who want clients out the door as soon as they have came, even if they have came within 15-20 minutes but have paid for say 1 hour.
I am probably wrong but I believe how they work is they will have another client lined up who when they give the green light can get to them quite quickly, therefore seeing two, possibly three clients in the hour but being paid per guy for 1 hour, so 3 hours money for 1 hours work.
Of course by doing this there is a chance of peeing off the wrong person.