Why 30 or 60fps, but never 48, 50, etc... ?

[Amnesia]

haxxiy said:

Most TVs and monitors have a fixed refresh rate, often 60 Hz these days.

If a game runs at, say, 48 FPS, some frames would be doubled every second, and some won't. The resulting video would seem more jittery compared to 15, 30 and 60 FPS, where frames can be doubled or quadrupled evenly.

That's why FreeSync and G-Sync monitors are a big deal to enthusiasts, they avoid this issue for their refresh rates are exactly what's being rendered.

But every modern TV today are not at 100 or above ?