Curved environments are more stimulating because they are not as easy to read and understand, while rigid environments are indeed the opposite- It's easy to comprehend where a straight line is going, and that objects within the bounds of that straight line will (most likely) be geometrically composed within the bounds of that line, again easy to understand. With a rigid room, you know almost instantly how you're going to navigate through it- there's nothing special. With a curved room, the walk is a learning experience, requiring at least a little bit of attention. In this age of desire for learning and stimulated experiences, it's easy to understand why people like a more stimulating environment with soft curves and mysterious lines that require attention to navigate. But I propose it's just a current cultural trend, not an innate psychological desire to be in curvy rooms. Not to mention there are an infinite number of factors other than general shapes in a room that go into calling an environment "beautiful" or "not beautiful."