One of the biggest shocks for me when I first came to Japan was learning about the stigma of non-separated toilets and bathrooms. Here, a bathroom that has the toilet in the same room as the bath/shower area is considered extremely unhygienic and when people are apartment hunting, there’s a search option that allows you to look at listings in which the toilet and bath are separate.
In America it is completely normal to have the actual toilet in the same room as the shower, and not much is thought of it. But in Japan this situation is not ideal. People believe that the toilet is a dirty place, and the bath is where you get yourself clean. To have these contrasting things in the same room is counterintuitive.
In Japan, bathing rooms are kind of special. Most people will wash their bodies outside of the actual tub, a practice that will make the entire room wet. They will sit on a small plastic stool as they lather up and rinse off. And only after that will they enter a pre-filled tub to soak for a while. A lot of space is required and there will be splashing. This is why it’s best to have the toilet separate, so it and the floor beneath it does not get soaked.
This is just another custom that has raised my standard for personal hygiene, and now I myself prefer to have the toilet separate from the bathtub. Japanese people might be shocked to go to foreign countries and find that this luxury does not really exist though.