But there's a flaw not mentioned: it presupposes that everyone has somewhere else to be. In America, the minimum wage generally doesn't pay for a one-bedroom apartment. So where are people living? Many are stuck in studios: one room with a bed, a kitchenette, and a tiny bathroom. Most of those are about the size of a normal bedroom. Obviously, someone who doesn't have a separate bedroom and living room cannot reserve the bedroom only for sleep and sex. So the treatment is only feasible for people above a certain living standard, just as it is also feasible only for people able to establish a regular routine.
Now flip it around. What if the structure of living space raises the risk of insomnia? By forcing many people to live in or near their bed, society could be running up the rate of a ruinous health problem. This could be right up there with things like artificial light and city noise as a contributing factor. I'd love to see a study exploring whether housing size / shape makes any difference in rates of insomnia. But to get away from the socioeconomic factors, you'd have to isolate a group of people for a while and then mix them around in different apartments. That's hard.