How so? A couple (of people) derives from the same meaning of the word couple, meaning two. It's the exact same context as comparing a couple of anything else.
"Couple" implies a specific sort of relationship between two people—there are lots of pairs of people, even pairs who know each other, that we would never refer to as "couples"!
That's a distinct meaning from "couple" as in "couple of apples", where it really does just mean "two".
I think what’s happening here isn’t really regional at all. It’s a kind of confusion that can happen anywhere within the Anglosphere. We have a word, “couple” which means exactly two things. But unlike “one” or “two”, children don’t tend to ever actually be directly told that “couple” means exactly two things, they just pick it up naturally.
People like playing with language, and use understatement regularly. Unlike “I’ll just have two beers”, where it’s obvious to any child who has learned to count that this is the case, when kids regularly see people around them say “I’ll just have a couple of beers”, they assume couple is another word for an indeterminate small amount like few. When they later learn of other uses of “couple” they assume these are unrelated.
Lexicographers can be frustrated all they want. People do indeed "like playing with language."
Sometimes one may want to be accurate but not really need to be precise. Sometimes one needs to be both accurate and precise. One should never be precise and inaccurate (e.g pi=8.739216503).
But sometimes people need to be vague and ambiguous (e.g diplomacy) and sometimes one can be ambiguous with another who knows exactly what he means.
Sometimes the gap is easier filled with non-verbals. If a waiter asks me if I'd like fresh ground pepper on my salad he doesn't ask if I want one twist, a couple of twist, few twist, or several twist. He starts grinding the pepper over my salad and says "Say when".
On the other hand, my wife has no need to ask. She knows I mean sex. (You didn't see that coming. I jest, but a couple has several ways of saying sex without saying it, some fewer than others.)
Sure, but I'm talking about the etymology and origin of the word couple as in people, which derives from the same word as couple, as in two. I'm not saying anything about the sociological relationship of a couple versus a pair of people.
Your etymology is correct, but that has no bearing on the fact that the word has multiple distinct meanings, which is very typical of English. It actually has at least three:
(1) A small number of things (roughly 2)
(2) Two people in some sort of relationship
(3) to join or connect (two) things together
Even though each is obviously derived from the fact that two things are involved, that wouldn't even cross the mind of a native speaker hearing the word in different contexts and assuming the right meaning.
“I only had a couple of beers, officer.”
“Hey, can I borrow a couple bucks?”