This may be the view of some foreign tourists in Japan, but the Japanese view yukatas as both sleepwear and hotel wear not only at Ryokan, but also at Japanese city hotel chains. For example, you will see people wearing them in the dining rooms (usually at breakfast time) of city hotels such as APA or Dormy Inn or when walking around the hotel, even the lobby lounge. What was being debated above was whether high-end Western-style hotels such as the Grand Hyatt, Ritz-Carlton, etc. (which follow a more Western than Japanese standard when it comes to dress code) allowed them to be worn in dining rooms or club lounges. As shown above, Grand Hyatt Tokyo has a written policy prohibiting the wearing of them in the Grand Club Lounge, and my experience has been that they are also prohibited in the dining rooms of these and other high-end Western-style hotels. But ryokan and city hotels are a different story and do not treat them as pajamas only to be worn in your room.