Centuries ago, "thou" was singular second person and "you" was plural second person.
"Thou" got abandoned and "you" lost its original meaning to replace "thou" as the new singular second person.
"You guys" or "y'all" are simply attempts to re-introduce a needed pronoun.
I think it's all just normal evolution of language. I actually think it's kinda neat how different English-speaking subcultures found different ways to reintroduce the pronoun.
The normal way for languages to evolve is for words to spread into different (adjacent) forms in order to express more nuances of their original meaning(s). The collapse of words' meanings, and for basic things as (nominative case) pronouns no less, like it happened in English for "thou" and "you", is not fitting the definition of "normal" in the larger context of linguistics domain.
> All y'all is used in the Southern United States when a speaker wishes to include everyone being addressed. Y'all may refer to an indefinite set of members of a group, but all y'all definitively includes everyone in the group.
Also, is it just me or does that Wikipedia entry have zero citations? I thought Wikipedia was allergic to citation-free claims..
I'm guessing it's regional and/or group specific.