I wonder. I'm sometimes mesmerized by hearing tales of people who sat in games with prominent designers at conventions at how little they followed the rules that they themselves wrote. I've heard similar stories about Tracy Hickman, Marc Miller, and many more. I also remember, from back in the days when I played Blood Bowl in the late 90s, how the Games Workshop studio hired a guy from outside, and he totally stomped everyone in the studio league because he actually used the rules that the designers themselves weren't using because of some unspoken gentleman's agreement to avoid utilizing certain rules very much. I do think that sometimes designers write products that they think are fun to write, and which are probably fun to read, but they lose sight of the fact that—in theory—they're meant to actually be played, and presumably played more or less as written.
I think that any time we write a complex set of rules there will always be bugs in the system and things we later wish we would have done differently. Authors of RPGs are human and are doing the best they can. They still make mistakes and change their mind on what's best.