Many homes that are designed for families with small children have two bedrooms that have a bathroom in between them. Having an en suite bathroom like this really makes it convenient for the kids and the parents. It is easily accessible for the kids and one less bathroom a parent has to keep clean.
Bathrooms don't seem to be nearly as important to kids as they are to moms, so the less you have to keep up with, the better. I like having my own bathroom not only for the privacy, but so I can decorate it the way I like and not have pink curtains or a shower curtain with colorful fish on it.