2 scents, thanks, I believe you and don’t need the source.
I was just wondering whether “only” chasidim have this minhag. Was it adopted by non chasidim in certain regions or not? It appeared to me that certain non chasidish (that some here would call heimish) relatives shaved. Maybe they cut their hair very, very, close, but that has always been my impression. Or they did it for practical reasons. I also remember once hearing this, but don’t remember the exact details. So can somebody please enlighten me further?