Why Don’t We Have A Plural “You”?

A number of readers responded to yesterday’s Monday with Mounce by suggesting “y’all” in Southern dialect (and ye, thou, etc. in King James era English) solve the problem of plural “you” in New Testament translation. 

But what about here in the Midwest, or other regions outside the South that don’t have an equivalent of “y’all” to turn to?

Presumably we had such a word at one time, if English from the KJV or Geneva Bible is anything to go by.

So why did those words pass from our language without being replaced?

I don’t have an answer, but if anyone reading this does please feel free to share. There must be a journal article or something out there that examines this phenomenon, particularly as it seems like such a glaring weakness in modern day English.