I think theres always a reason for the way things happen.
On the day my brother died my mum was supposed to be looking after all 3 of my kids.
Joe, my brothers son somehow ended up going to his other aunts for the weekend.
Dan my eldest came home for some reason I can't remember now.
James my youngest ended up going to help my aunt with her garden (and she very rarely has any of my kids)
Maybe it's your wifes HP keeping her out of things until she really needs to be there.