When you're a stay at home Mum and you do a babysitting swap during the day with a friend, you usually end up with time off on a weekday afternoon. And most times, you do something glorious and selfish, like read a book with no interruptions or drink a hot cup of coffee. But definitely something away from your child. And most often, alone. But when you are a working parent, and you have days off (ie Saturdays and Sundays) you spend all your time with your kids. So you never really get time on your own. And I bet that if you choose to spend time alone, there is at least an initial sense of guilt, like you should always want to be with your kids when you can. Which means that the vast majority of parents feel a little bit bad for having a good time on their own.
This whole concept is kind of blowing my mind right now.