Eli5: Why screen refresh rates are 60Hz, 90Hz, 120Hz, and 144Hz? Why not other numbers?
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Screen refresh rate for modern computer displays comes from the vertical frequency of old analoge color CRT TVs.
The NTSC standard used in places like the US had a frequency of 60Hz (technically 59.94Hz) and PAL/SECAM used in places like Europe had 50Hz.
They inherited that from the frequency of the electrical grid which is 50Hz in much of the world and 60Hz in parts of Asia and the Americas.
Meanwhile old analoge movie reels ended up standardizing on having 24 frames per second on films.
Since much of the old analoge content was in 24fps, 25fps or 30fps and the old TVs and computer displays worked with those frequencies, it made sense to have higher displays refresh rate in multiples of those existing standards.
If you have a source that is in 30Hz you just show each frame twice or trice rather than anything more complicated. (144 is 6 times 24 for example)
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