Biology is a factor because the sun isn't up. Also there is the desire to do things in the evening, such as a parent having dinner and interacting with their k

Biology is a factor because the sun isn't up. Also there is the desire to do things in the evening, such as a parent having dinner and interacting with their kids before they have to go to bed. Or to get home from work to help them with their homework. Or let's say as a parent I don't want to have to wake up at 6am because my kids have to wake up that early for school when I don't have to be to work until 9 or 10.