Education runs on a "morning person" schedule from a young age, through early adulthood. After that, there's certainly more choice available in terms of life schedule, but the vast majority of people are corralled into a form of employment built on the same schedule. Even if not, all major services one interfaces with in one's life operate on that schedule.

Even if you managed against all odds to develop healthy daily habits during the 20-ish years of strict poorly suited scheduling that is the education system, applying those habits only becomes more difficult when you move into a more independent self-driven environment of providing for oneself financially. This absolutely kills any hope of developing productive habits for most people.

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Anecdata: I'd classify myself as "not a morning person", but I don't find difficult to get up early. e.g. I don't need an alarm-clock. What I find difficult is functioning after getting up.

I don't have kids but I've a pretty demanding large dog that had a strong preference for 5am walks when he first arrived, which I adapted to reasonably easily. Walking a dog isn't really a "significant accomplishment" in the commonly understood sense, and more-importantly, isn't a mentally challenging or "applied" activity. I'm completely unable to function in the mornings when it comes to doing anything even mildly complex.

Also, getting up at 5am means I'm severely less productive from 6pm onwards, which is my peak productive period when I operate on natural rhythm. I'm reasonably successful (I think) and I work a remote job from Ireland on a US tz schedule, so that's particularly tough.