Those examples are the result of movie/series makers who just don't care about authenticity. Yes! it drives us crazy too. That's why it's the rather playful little "jokes" that I'm more interested in.

As an example of how silly it all becomes - a friend of ours played an extra in the latest film about Ned Kelly. The cast were told they were to shave off their beards because facial hair was unfashionable. Ned Kelly without his lush beard!!! At the last moment it was decided that the cast could maybe have very close-cropped beards and that's how it was done. It's no wonder authenticity in regard to the music is thought to be unimportant.
Cheers, Joy