From what I understand, cell phone usage has doomed manual transmissions in even high performance sports cars which have paddle shift automatic. People only have two hands, so one to steer, one to fiddle with the phone and none for the gearshift. Hands free via Bluetooth didn’t reverse the trend.
That’s part of it. The fuel economy is not better with a manual nowadays. (Or marginally so.) And many never learn how to drive one, because even the economy cars sold here usually have an auto except on the very bargain-basement trims.