My best guess about why that idea has so much staying power is that it's useful for consoling oneself after having been failed by mainstream language education.

My best guess about why that idea has so much staying power is that it's useful for consoling oneself after having been failed by mainstream language education. The people I know of who've successfully learned a second language that way are invariably characters on TV shows. Having spent much of the past few years of my life helping two small children learn their first language, I have my doubts about whether the "immersion is magic" approach is really even the most efficient way to pick up language number one.