One of the characteristics of film and film-on-video is its relatively low temporal resolution. Unlike spatial resolution (which has more to do with visual sharpness and —indirectly— pixel count), temporal resolution has to do with how many frames (or fields) are recorded and displayed per second. Standard film production is normally shot at 24 frames per second, which is a much lower framerate compared with traditional television, which has been 50 fields per second (in PAL countries) and 59.94 fields (in NTSC countries). One of the many ways to achieve that film look or film-on-video look is to shoot with low framerate progressive video, which is commonly referred to as “24p”, 25p, and “30p”, since all three of these are much lower than the original field rate of traditional television. Because of the conditioning of TV viewers starting in the late 1970s and early 1980s (when TV news switched from 16mm film to 3/4” U-Matic video), we tend to associate high frame (or field) rate video on TV (50 or 59.94) with live video, and we tend to associate low framerate video on TV as either documentaries or dramatic productions. Both “24p” and “30p” have that low framerate look, although the low framerate look is milder with “30p” than with “24p”.
I just noticed that the Canon XF100 defaults to a shutter speed of 1/24 sec when in 24p. Why they wouldn't default the shutter to 1/48, I have no idea.