I think the morning congestion is one of the biggest reasons for the doubling of bathrooms over the last 50 years. In the past, only one person was in a hurry t

I think the morning congestion is one of the biggest reasons for the doubling of bathrooms over the last 50 years. In the past, only one person was in a hurry to be washed and groomed each morning. Now there are at least two, and even kids are much busier than they were before. Another reason might be the accessibility of traveling. More people are used to staying in a hotel compared to 50 years ago, so when you have a guest you would want to offer them a comparable experience. That includes a private bathroom as you said. Both of these trends are common to most parts of the developed world, but people in other countries don't have as much space to actually go ahead and build more bathrooms.