The best reason to use 36 frame rolls, is that they fit perfectly onto a single 8x10" contact sheet, no wastage.
If I'm ever going to short load, I use 18 frames and cut an 8x10" sheet in half on the long side.
I do this with colour and B&W.
On the subject of bulk backs for 35mm film, the modern ones produced in the late seventies and eighties by Nikon and Olympus were 250 frame, the internal film holders and their loading systems are able to be used in either camera.
One of the main uses I knew for these 250 frame backs was school photography. One company I knew of had about 10 of these fitted to Nikon F3 HP bodies. That company had the most knackered F3 bodies, I have ever seen!
The power drain of these big backs is quite enormous so some of these were fitted with a mains power supply to the MD4 motor drive.
I was involved in a television advertisement where we cobbled together an F3 body, MD4 drive, 250 frame back, 20 film cassettes, mains power supply MA4 (which required an additional plug that was only available from the USA as Japan had none) and 500 x 100' rolls of B&W film (kodak, don't remember what)
We converted a cibachrome roller transport paper machine to process the film. IIRC we set it up to process 6 lines of film side by side.
It took us about 4 weeks to get all the equipment together, a couple of days to ascertain that everything worked, then we were ready.
We shot a young woman pretending to shave her legs with brand X lady shaver so many times, the poor girl started to cramp up. To keep things going smoothly, we slung a handy female with quickly manicured hands, horizontally in a canvas sling to continue the shaving motion.
We were at the studio at 3 am and didn't get out until midnight.
All of this effort eventually went on a nation wide TV campaign and out of the 30 seconds that the ad ran, we accounted for less than 4 seconds.
Man there was money being thrown around then.
The biggest magazine back I have ever heard of was for the Nikon F2, it took 30m of film for 750 exposures, I haven't ever seen one.
Mick.