'Cause, computers? I imagine that video frame rates were never a big enough issue for computer manufacturers to be concerned about them. For a long time, computers didn't have any video playback capability. They just picked one refresh rate and went with it, higher being better. Of course computer and monitor manufacturers were predominantly American and Japanese (both 60 Hz countries, at least in parts), which may have been a factor.

At playback time frames will be repeated as necessary to get from 25 fps to 60 fps. For each second of video, 15 frames are played twice and 10 frames are played 3 times. It amounts to a 2:3:2:3:2 pattern of repetition, though it's actually dynamic and determined automatically by the video subsystem, not the playback software.

For 24 fps content played at 60 fps, it's similar: 12 frames in each second are played 3 times, and 12 are played two times, in a 3:2 repeating pattern. It's called 3:2 pull-down.

When the playback frame rate is much higher than the content frame rate (by a factor of roughly 2.5 or more), our eyes aren't too sensitive to the repetition or its pattern. At smaller ratios, irregularities in the repetition pattern can become noticeable, so the repetition should be kept regular or avoided altogether by blending or interpolating frames. Converting from 50 fps to 60 fps, for example, doesn't look good when it's done by repeating frames.