From World War I onward, saving energy by using daylight instead of artificial light for more of our waking hours has been one the main justifications.
The body begins preparing in the hour before you naturally wake-up, body temperature rises sleep becomes lighter and hormones such as dopamine and cortisol are released which give you energy to start your day.
The research community in supportive play is so resounding, I would expect to see children in nearly every household, every preschool and kindergarten classroom playing for most of their waking hours.