My wife always complaint that shee needs time for herself.?

Me and my wife have been married for 5 years with two kids one of the them is my stepson which I love like he was my son and the other one is my son. On the long weekend coming up she had decide that she wants to go to her sister's house in another state. Her sister have kids plus a husband. I thought that as a family we were going to plan something together but NO she says that she need time for herself. The only one that goes out by herself once a month or once every three months is her and when I go out I like to go out with her NO because she doesn't let me go out by myself is just that I like it that way. We both do the same amount of work at home we both (COOK, WASH CLOTHES, TAKE CARE OF THE KIDS, etc