Taghlib can express two different members concisely under an established shared form. Al-abawan replaces a fuller coordination of father and mother; al-qamaran similarly names a pair under a familiar dual.
Yet brevity is not the only point. Al-qanitin conveys membership in a broad class; tajhalun preserves direct address to the audience.
Using a predominant verbal perspective for a contextual effect makes taghlib a rhetorical resource, not only a morphological pattern.