it's a good question i've asked before too. basically it's a licensing issue, if the shop is open well past 8pm then people will know that there's more than just massaging going on there and the shop can be very easily called into question. I completely agree with you though, i normally get the urge late in the arvo or late at night. In my experience they targeet locals or people like me who work from home and can sneak off during lunch time