They belong to some kind of strict Southern religion where they don't even believe in the first kiss until the wedding ceemony!
So I have a feeling that Michelle stays on her back because of the Bible scripture that says the wife must give the husband his due are whatever the heck it says. So I guess she does it for good ol' Jim Bob. . !
Where the heck is Lorena Bobbitt when you need her ! She needs to meet Jim Bob on a dark road one night !