I sometimes bracket color slide film, since there can be a range of about 2/3 stop where the exposures might all be "correct" but the emphasis or emotional quality will be different.

I don't bracket B&W, but if there is a scene where I'm a bit unsure as to how much contrast will really look good at the printing stage, I'll expose a second sheet and keep it in reserve, though in the end the first development time is usually right, and the reserve sheet serves as a safety sheet in case the first one gets scratched or some distracting element walks into one of the versions.