Very few frequent business travellers fly Saturdays, but many infrequent and/or clueless passengers do. This tends to make lines for check-in and security screening move much slower. It can be very frustrating to get behind a family travelling with all their worldly posessions who can't seem to empty their pockets and have to keep going back and forth as they set off the metal detector.

It also clogs up the boarding areas where folks tend to stand right by the gate even though they are not ready to board.