Hello Wid0maker!!!
I wouldnt say never use it. firstly its horizontal GI frames activate 1 frame sooner than baseholds does. on top of that it is much easier to execute from crouch than iRCC B+K, and because iRCC still takes time, 66A still comes out faster.
on top of that the damage you get off it, isnt HORRIBLE, though it isnt great, but it does re-zone the opponent out pretty well on successful aGI, which makes it rewarding in its own sense.
its really a matter of pick your poison - do you wanna rely on stance roulette and risk of CH if your opponent guesses right? or do you wanna simply take your WR punishment and go on about life?
personally here is how i use things:
I use things like B+K ~ SBH aGI for things that i can react to. slow horizontal lows, chargeable guard crush mids like say, asta 44A, and even sometimes strings if i feel they will finish them.
I use 66A if i need an aGI from crouch, or if im under pressure and i expect a horizontal, for some other strings that B+K will either not be fast enough for, or that i need to aGI from crouch, and very rarely depending on my opponents habits, i might use it as an advancing move if i expect a horizontal.
and of course both of them can be used in an attempt to make a read on 2A mashing.
of course because it is so slow and reactable, you dont want to ever try to use it as a step kill or the like - you're just giving the opponent free damage otherwise.
but its all up to your judgement where and if this has a place in your game. personally I have found niche use for this move in the past, and so long as a proper situation presents itself, I will use it again from time to time.
I hope this helped you with everything you needed to know! ^-^ feel free to ask anymore questions you may have!