This is pretty common for people in other parts of the world (Asia, notably). IIRC, it was kind of normal in Western nations during the Victorian era. In North America today, there's this culture of independence and individualism which would rub many the wrong way to have their in-laws/parents living with them all the time.

My own in-laws stayed with us a few times for a couple months at a time. I must admit the level of shenanigans my wife and I normally get up to was much lower during that time, even though I thought it was nice having them around for a while. Relationship dynamics are probably a major factor here, as well as personality types.