Why do japanese hotels actually make you pay by the person? i was wondering the actual reason.?

Question:

I have been living and traveling in Japan for 3 years. When I had a girlfriend in Nagoya, I used to stay at a hotel in the city. It was a 1-person room. Because she lived with her parents (at 23-years old) we would use,my hotel room to do what we did. When I got the room, girlfriend with me, I told them I only want a 1-person room. They looked at me like I was nuts and gave me the room. Never heard anything more about it.

While I was in Gunma I got a 1-person room and met a girl at a club. According to her, we had to go into the hotel 1-at-a-time because I had a 1 person room. If I walked by the front desk with a girl, they would have me switch to a 2-person room. I don't plan to meet girls when I go out so I don't pay extra if I don't have to.

Then while I was in Tokyo I had met a friend from Okinawa for some drinking and dancing. Her 2 friends came along. I had to rent out 2, 2-person rooms. In the US, if you could sleep 10-people in a 1 person room it was,no big deal. So my question is, why? Is it because a 2-person room has more space or is it an actual rule that I could get fined for?

Answer:

There is a rule in Japan that "1-person room must be used by one person".

One reason is that 1-person room in Japan is really as small as only for one person. And another reason is, as another says, hotels want you to pay for 2-people room if you are 2.