We can blame Thomas Edison. Also, there is a certain regard for hard work and long hours. Henry Ford frequently boasted he slept only four hours a night, but after his death his housekeeper disclosed that he usually fell asleep at his desk in the afternoon. Part of the reason is that when people go to sleep at night, their thinking, judgment and memory are impaired. They don't know that they snore or have sleep apnea, or that they turn over 12 times an hour, or that they talk in their sleep.
Insomniacs tend to spend too many hours in bed, which is maladaptive.
Long times in bed perpetuate poor sleep efficiency and lead to more fragmented sleep. There are many other examples. There is a view that poor sleep cannot be an illness and that treatments are analogous to cosmetics. There is a misconception that somehow you are in control of the amount of sleep that you have, and that, in any case, if you don't get enough, it's not viewed with the seriousness of a life-threatening illness. There's a misconception that sleep disorders don't have a long-term negative effect on the patient.