The short answer is "backwards compatibility". The long answer is... well, it's the rest of this video.
MORE BASICS: https://www.youtube.com/playlist?list=PL96C35uN7xGLLeET0dOWaKHkAlPsrkcha
Written with Sean Elliott https://twitter.com/SeanMElliott/
Graphics by William Marler https://wmad.co.uk
Audio mix by Graham Haerther https://haerther.net/
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