Why salt AND pepper and not salt and/or pepper Which is to say--narrowing things down--do the two actually have any mutual enhancement effect, such as, say, in the manner in which salt can fool the tastebuds into perceiving sweet as even sweeter? (thus reducing cost for sweetening)

I have never "observed" any such effect of salt and pepper used in tandem...at least I don't think so. Is it simply that the two are typically found together, and handily so, in most any food prep area? (The recommended reading elicited by the question suggests such an interpretation but does not address the aspect of s&amp;p mutuality when shaken, used, or tasted together)

If there is, in fact, no such mutual complementary effect, it will suffice to simply say so--I will accept that as an equally affirmative answer.
Pepper is likely just lucky to be a very commonly used spice that gets to hang with Salt all the time, though Salt really makes everyone else look good anyway.  Pepper just doesn't look good on its own.

Uh... Yeah.

I say you do see salt paired with plenty of other spices, but because "Salt and Pepper" is pretty engrained in our culture (refer to the potential duplicate thread), you don't really take note. Therefore, you will always see "Salt and X" as a matter of fact but rarely do you see "X" alone without that ever so essential Salt.

This answer's getting pretty close to the Answer in the other Salt and Pepper question, huh?