There was a great post explaining this a couple years ago but I can’t find it now. Without details, it came down to having to have a system that interacted properly with all sorts of different components from the PA system, cockpit to cabin comms, cockpit intercom, VHF radios, and all their associated microphones, speakers, amplifiers, and transceivers. To tie all these together needs compromise. To overhaul it all with new technology is just cost prohibitive at this point, not to mention ground to air communication is still analogue VHF AM.

ETA - here’s one related post: https://www.reddit.com/r/explainlikeimfive/comments/nliql6/comment/gzium0a/