I’ve always understood “y’all” to be an example of the English plural entity. Referring to an individual as “y’all” implicitly assumes family and neighborhood associations.
Think of “y’all” as “you and yours.” This makes “all y’all” a plural, plural entity, addressing multiple individuals with implicit associations. A well-placed “all y’all” can cover a whole county in the south with a mere two words.
It’s actually a very sophisticated term as a result.
Yes, I think ‘y’all’ and ‘all y’all’ too (as silly as ‘all y’all’ may seem when you stop to think about it) are useful and add to the expressiveness of the English language.