so you mean, ignore the fact that people have funny quirks?
i would like to think that acknowledging that people effectively have their own perculiar habits, and informing them that everyone is different, that is a fact.. is being entirely rational AND logical. just removing it because it doesn't seem to suit your logic or rationality (or whatever version of it anyways) seems delusional to me.
if life was that simple, we would all know how to implement policies, and anyone could be a successful politician since people are all rational and adhere to logic. but they are not, and they don't, do they?
you see, effectively by your definition of manual mode coming into play, it literally declares that logical people would not use manual mode UNLESS the camera metering is insufficient for the situation and fooled by the scene. but no, manual mode allows you to adjust BOTH shutter speed and aperture simultaneously, that should be the technical definition of all technical defnitions, nothing to do with eye or reference to camera meter. manual mode allows you to achieve stuff that av mode and tv mode would not allow you to, like extreme exposure of a scene (not just for hdr, mind you, but also for say, high key.. would you say that when forced to shoot manual for high or low key, the camera metering has failed? no, it has not in actuality).. or extreme underexposure of a scene as you see fit.
there are also practical reasons, which could be loosely pigeon-holed into "quirkiness", like a certain need for control over BOTH settings, instead of one at a time. that in itself is the most primitive essence of manual mode, if you ask me.
that is vastly different from your.. if you permit, quirky definition and understanding of manual mode.. which seems ironic for one claiming that quirkiness has no room in a logical/technical discussion. quirkiness is here to stay, be it in man or machine.. like it or not. some people just feel a need to have more control over the tools they have.. which is why even though automobile technology is sufficient today, there are still manual cars available in the market. same goes for manual mode in cameras, essentially some reasons are no different even though the tools/machines differ.
p.s. if anything, i suppose arguments of individual viewpoints here in this thread, is certainly, not going to help anyone arrive at any conclusion other than the fact that you and i are immensely bored.