This gets my goat, too. I don't begrudge parents time to themselves but there is no way they need to leave a child, from open to close, every time they have a day off.
In my case, dcg2 is left here for almost 11 hours a day, whether mom and dad work or not. They never pick up early and I can count on one hand how many times they have kept her home willingly in the year and a half she has been coming.
This child is also pawned off on grandparents on weekends.
Guess who has the most behaviour issues?
I feel badly for the kids and for the parents. One day they will realize what they missed out on. Maybe.