alt Hacker NewsA better example might be why we build stairs with a standard riser height and tread run. If you've ever accidentally tripped on an unusual or non-standard stair, you already know this.
Users don't need to think about how to use them; they are ubiquitous and familiar, and therefore intuitive and automatic.
If every set of stairs (or, worse, if every stair in a set) was radically different, every time you approached some stairs you would have to think carefully about how to use them so you don't fall.
Your point is true, but the one I was replying to was focusing on the aesthetic aspect. For them, the sameness of UIs, while functional, make for a drab experience.
My point is that I don't find this to be case. Rather, consistent UIs, while functional, are also beautiful to me. The constituents of the UI can be designed with aesthetic taste, but the way it is all put together consistently and functionally has a beauty all its own.