Why is TV frames per second?

I look at the historical quirks which gave us TV at frames per second. In North America at least. It’s a comfortable 25 fps in Europe. More on that thing I mentioned at the end of the video here: Here is the spherical video I was making with Henry Segerman which made me research NTSC frame rates in the first place: Yes, technically, if you divide 4,500,000 by 286 you get a horizontal frequency of 15, lines per