Once upon a time, all photographers have no choice but using FILM. In those days, editing can be done only in the darkroom, which was not very easy (especially for BW films), plus they were doing it with the help of stopwatch and mask only (expose this part longer while covering the rest with a mask, and repeat for other area). They can't see the result until the print goes into the fix bath, washed with running water, and hung on the line and they turn on the light.
For those who doesn't have access to a darkroom, bracketing was very useful, and also wasteful. For example if someone bracket -1,0,1 (using f/stop and/or shutter speed combination) it means he expect that out of the 3 shots, at least one gives him the result he wants. Those who use a better camera, he can bracket -1,-0.7,-0.3,0,0.3,0.7,1 with the hope that one in those seven shots gives him the best result.
To do white balance bracket, usually they used color filters with different strengths, and once again, one exposure for each filter.
Nowadays, we can edit our photos digitally. So bracketing was not popular with digital photographers, even ts is still quite useful in some ways.
The other knowledge that is going to lost in the digital age was the push/pull film processing. I remember when I am learning to use a film (can't remember the name... more than 10 years ago) which was rated ISO 640 but can be pushed or pulled between ISO 200 - ISO 1000.
Those were the days...