For a long time, one reason for shooting at 23.976 fps was because that post was done using NTSC video transfers, so even if you shot film at 24 fps, it was transferred at 23.976 fps to video for distribution to editors at 59.94i. And generally sound editors would receive videotape copies of the offline cut and edit to that. In the end, the whole thing had to be resolved back to straight 24 fps for feature films.
And once 60 Hz countries chose to continue 59.94i for 1080 HDTV broadcast, the problem really hasn't gone away.
I did one of the first 24P HD movies on the F900, "Jackpot", in 2000 and the Sony F900 had the option of 24P or 23.98P... I chose 24P. Later I asked how the sound mix was going and the editor told me that they had to shift whole reels over slightly to get them to stop drifting in sync, so I suspect that was partly due to shooting in 24P instead of 23.98P but editing in NTSC. Of course editors can now work in true 24P and they can send that to sound editors who can work at true 24P on their systems, but for some reason, the whole chain still works using dubs in 59.94i.
