Can't speak for anyone else of course, but before kids a day with no obligations was mostly just a nice day. With kids it is so much more significant.
My colleagues that don't have kids, they waste their time. Not by doing nothing - that would be awesome - but by creating problems for themselves that end up taking their spare time. It is like they believe they will always have empty days to spare.
You know your perspective also works in reverse. When I was young I wanted time away from my parents. Now that they're gone, I would love to spend even 5 minutes with them.
