The United Baptist church (just a bit more primitive than primitive baptists) my grandfather grew up in, and later centered his life around, eschewed the use of musical instruments to accompany the voice. I grew up to the sound of his wonderful mountain voice singing a capella hymns, or to his clear and accomplished whistling as he tended his bees and his garden.

I sing a capella because I don't have the confidence to ask and expect instrumentalists to play for me and adapt and arrange to my voice and key, but most of what I sing is music that is usually accompanied.

But I also love a capella voices and song, whether it be a ballad singer, a street corner group of guys or gals singing doo wop with richly layered harmonies. an individual, duo or group singing work songs and chanties, or high church latin chants.

The human voice is a lovely emotive and evocative instrument, accompanied or not by musical instruments.   We sing unaccompanied for many, many reasons. Just as we sing accompanied for many, many reasons.

It is all good. It is all the expression of who we are as individuals and of what we are as a species.

(and I just realized that my response might sound like I think you are challenging the worth of a capella music.   I don't think that at all. It is all good.