It’s called copula deletion, or zero copula. Many languages and dialects, including Ancient Greek and Russian, delete the copula (the verb to be) when the context is obvious.

So an utterance like “you a bitch” in AAVE is not an example of a misused you, but an example of a sentence that deletes the copular verb (are), which is a perfectly valid thing to do in that dialect, just as deleting an /r/ after a vowel is a perfectly valid thing to do in an upper-class British dialect.

What’s more, it’s been shown that copula deletion occurs in AAVE exactly in those contexts where copula contraction occurs in so-called “Standard American English.” That is, the basic sentence “You are great” can become “You’re great” in SAE and “You great” in AAVE, but “I know who you are” cannot become “I know who you’re” in SAE, and according to reports, neither can you get “I know who you” in AAVE.

In other words, AAVE is a set of grammatical rules just as complex and systematic as SAE, and the widespread belief that it is not is nothing more than yet another manifestation of deeply internalized racism.

I love linguistics! 

Heck, it’s COMMON. In addition to Ancient Greek and Russian, Semitic languages, Celtic languages, and some Southeast and East Asian languages do it. 

Some Semitic languages still make do without a present tense form of the verb “to be.” 

I’m having a hard time, now that I think of it, coming up with circumstances in which the present tense of “to be” is actually essential to communicating meaning. 

TL;DR: AAVE’s copula drop is basic efficiency that a ton of other languages already do.