Asklemmy

I think 30fps (25fps in PAL-land) became the standard because televisions were 30 FPS (NTSC) or 25 FPS (PAL) due to interlacing. While the screen redraw on a NTSC television is 60 per second, it's done as two fields so you only get 30 actual frames per second. This was done so you could have a decent resolution (525 lines for NTSC or 625 lines for PAL) while maintaining reasonable RF bandwidth limits for the TV signal by sending a single frame as two fields, half of the picture in each field on alternate TV scanlines.

So you probably have a lot of industry inertia to deal with so 30 fps (or 25 fps where PAL was formerly the standard) ends up being the standard. And for video it's good enough (although 60fps/50fps is still better - until fairly recently, this would entail too much bandwidth so sticking with the old NTSC or PAL frame rates made sense).

But for computers no one really used interlaced displays because they are awful for displaying the kind of things computers usually show (the flicker is terrible with a static image in an interlaced screen mode. While it's true there were some interlace modes, nearly everyone tried to avoid them. The resolution increase wasn't worth the god-awful flicker). So you always had 60 Hz progressive scan on the old computer CRTs (or in the case of original VGA, IIRC it was 70 Hz). To avoid tearing, any animated content on a PC would use the vsync to stay synchronized with the CRT and this is easiest to do at the exact frequency of the CRT and provided very smooth animation, especially in fast moving scenes. Even the old 8-bit systems would run at 60 (NTSC) or 50 (PAL) FPS (although 1980s 8-bit systems were generally not doing full screen animation, usually it was just animating parts of the screen).

So a game should always be able to hit at least 60 frames per second. If the computer or GPU is not powerful enough and the frame rate falls below 60 fps, the game can no longer use the vsync to stay synchronized with the monitor's refresh, and you get judder and tearing.

Virtual reality often demands more (I think the original Oculus Rift requires 90 fps) and has various tricks to ensure the video is always generated at 90 fps, and if the game can't keep up, frames get interpolated (see "asynchronous space warp") although if you're using VR if you can't hit the native frame rate, it's generally awful having to rely on asynchronous space warp which inevitably ends up distorting some of the grpahics and adding some pretty ugly artifacts.