Bass Clarinet in A? Why?

Why is there a Bass Clarinet in A? Does anyone have one? What are/were they used for? Today I got a question from a YouTube viewer about the instrument:

I was wondering why there is such a large collection of music written for Bass Clarinets in A, but the instrument is never played. Why do clarinetists readily switch between Soprano Clarinets in A and Bb, but shy away from this practice on Bass Clarinets? Can you share some of your thoughts on the Bass Clarinet in A? Would you play one if it existed today?

My answer is this: Bass Clarinet in A is definitely an enigma, and I honestly don't have a good answer to your question. The truth is, there are VERY few Bass Clarinets in A available in the market—in fact it was that reason that the bass clarinet initially was fitted with a low Eb key, so people could transpose Bass Clarinet in A parts (Wagner) and still be able to hit that written Low E (which of course on a Bb clarinet would be a low...Eb!)

It's not about shying away; it's about the fact that it's a very expensive way to support a very small repertoire of music. I've played one, and it wasn't all that great (probably the instrument, not the fact that it was in A).

So, do any of you have a Bass Clarinet in A? Do you use it often? What's different about it from a Bb Bass Clarinet?