stereo has been the default way to record audio for the last 80, 90 year
No it hasn’t been. 70yrs would be a stretch. Even in the 60s you’d still have Mono albums released regularly, as well as alongside Stereo releases. Stereo television broadcasts weren’t introduced until 1984 in the United States. For reference, the first Dolby Surround cinema release was Apocalypse Now in 1979.