Getting to bed early is not a complex issue - you're right. But actually getting QUALITY sleep is very much a complex issue.

Not only sleep apnea, but you can have trouble sleeping for other undiagnosed (and hard to diagnosed reasons). For example, you may suffer from adrenal fatigue, too high/too low cortisol levels, or chronic stress that can lead to early morning awakenings. You can suffer from nocturnal asthma. You can suffer from restless leg syndrome. You can suffer from COPD or some other pulmonary issue.