If you start thinking of the way roads work as part of the user-interface for driving, then it is straightforward to see why occasional one-way streets are problematic. Consider how clickable-things worked in Windows 7. Sometimes, to get something to ‘go’ in the relevant sense, you would click twice on the thing. Other times, you had to click just once. This caused significant confusion, because it created an inconsistent interface. Similarly, when driving, if roads interface usually one way, but then switch to another way occasionally, it can cause similar confusion and frustration for the user (i.e., the driver).