I can understand people just fine with the voice profiles provided by Bluetooth. Strictly speaking, I don't need anything better than that.

But it sure is nice to be able to make phone calls where people don't sound worse than they did with digitally-switched analog landline telephones in 1995. Bluetooth doesn't get there at all.

The losses of Bluetooth even compound generationally: The inescapable tin-can audio of Bluetooth at one end first gets transmogrified by at least one intermediate lossy codec for transmission across/betwixt the network(s), and then gets tin-canned harder when the far end of the connection is also using Bluetooth.

For perspective: 1995's phone calls were ultimately limited by the G.711 codec, which itself dates to 1972. I'm not setting the bar very high here at all.