Linguists have always been tempted to explain language change by appeals to economy of effort (alias the principle of least effort) whenever the latter seems plausible, but the meretriciousness of such explanations is also easily detected. A good case in point is abbreviation, i. e., the appearance of a shorter form of a word or phrase.
As has been illustrated in more than one earlier post, clear cases of functionality involving economy of effort aside (what sane person would say “the John Fitzgerald Kennedy International Airport, please” to a cab driver instead of “JFK, please”) when a word or phrase is shortened, the most common stylistic outcome is the creation of emotive or affective value by comparison with the original (unshortened), neutral form, an outcome that is especially prized in advertising (both print and broadcast). This applies to acronyms as well as other types of abbreviation. However, when acronyms or other abbreviations become so common as to efface their unabbreviated progenitors from most speakers’ memories (take NATO, for example), what originally could have been ascribed to economy of effort as well as to a stylistic impulse fades from memory and assumes common currency without an attendant stylistic value. This is what happened over time, for instance, with knickers < knickerbockers.
Abbreviations continually arise in spontaneous speech, and these neologisms typically need time to take hold. Here is a contemporaneous example extracted from a real-life speech scenario involving the recent introduction of grands as an affective (emotive, hypocoristic) derivative of grandchildren. When a trainer in his twenties used grands in a sentence inquiring after the progeny of his seventy-two-year-old client, it took even a linguistically sophisticated auditor to request a restatement of the question before the trainer’s meaning became clear, as the client was encountering grands for the first time.
The point of this exchange has nothing to do with economy of effort and everything to do with the semiotic value of abbreviation, which is typically affective. The trainer’s choice of grands instead of grandchildren (thankfully, not the odious grandkids) was clearly in the service of expressing a shared attitude of endearment grounded in an abductive inference (in the Peircean sense) that the designation of the client’s progeny with a hypocoristic abbreviation would be stylistically more appropriate in this informal context than would the unabbreviated, linguistically neutral form.