Many moms have young children and are up multiple times a night. They then are up at 6 or earlier to get ready for work, geet older kids up, etc.
I am not saying they aren't tired, but it's hardly uncommon. Sleeping in, naps, etc simply is not an option for a huge number of people.
It might not be an option, but we all have choices and sometimes earlier choices and decisions reflect on our options later.
Wouldn't make any difference to me though, I have the opportunity and I'm an awful napper and feel like cr@p if I even Could fall asleep in the middle of the day.