Can comp this. I tend to sleep very badly during the week at times and Saturday is a catch-up day for me, when I usually sleep well into the afternoon.

Having a chance to "reset" during the weekend helps me more mentally than it might help physically. Deep sleep has been described to work as a scrubber of sorts, so longer periods of deep sleep should help with scrubbing all that mental cruft away.

Plus just being able to relax goes a long way, knowing you have to be somewhere by certain time always puts some weight on you that can negatively impact your sleep.