Great question! When I was married it used to be on the weekends that were set aside for “afternoon naps.” It was easier when kids were also napping or it was time to turn on a movie for them to watch. I was too tired and in no mood at night. In Japan, you have this culture it love hotels where you can rent a room for an hour or more to have sex. This was also because houses tend to be small with no room for privacy.