Mike Suomi is the principal and vice president of interior design at New York-based firm Stonehill Taylor, which counts brands like Hyatt and Hilton among its clients as well as boutique properties such as the Nomad Hotel and the Refinery Hotel. He says the trend is driven by a number of factors, including hinting at a spa-like atmosphere to enhance the guest experience. But primarily, he says, opening up the bathroom to the rest of the room creates the illusion of more space.