"Wasn't there a company making cabinets out of cast concrete?"
Maybe you are thinking of different brand, but early Hales speakers had concrete baffles. Paul Hales switched to MDF because of economy in creation and exporting the heavy speakers. I came across an Asian manufacturer making cabinets out of vases. They were trying to find US distribution. Nice people; I hope they didn't struggle too much before quitting the impossible mission of marketing it to US audiophiles.
MDF, if anything is ultimately practical and established. I have not heard a wood box speaker using Scanspeak drivers as good as what YG has achieved, and I welcome the variety and pioneering as MDF is not some panacea.