During my early film photography days (late 70s and the 80s), I generally carried two Nikon FE (later FE2) cameras with me - one for B&W and one for slides (I had a black body and a chrome body, just to make it very easy to keep track of which was loaded with what film). If I happened to be shooting just one type of film, I often still carried them both, so as not to have to constantly change lenses.
Why two of the exact same model? I really liked the FE's viewfinder display, and with two identical cameras I didn't have to switch back-and-forth between different displays. A minor detail, perhaps, but it just made the photo-taking process a bit smoother. My initial second camera was an FM, chosen because I wanted an all-mechanical body as a back-up to the electronic FE. But after awhile I realized that if I were going to have two cameras with me most of the time, there wasn't really a need for one of them to be mechanical - after all, the odds of two FEs both losing battery power at the exact same time, when I had no spare batteries in my case, was pretty much zero. I like the FM/FM2 - it is a great camera and I do appreciate its all-mechanical operation - but on a daily basis the viewfinder factor took precedence.
Now that I am back to film photography after a 15 year break, my reasons for multiple bodies of the same model are a bit different. The cameras I prefer to use - the FE2, the F2, and other Nikons of that era - are now 30 to 40+ years old. The are well built and many are still functioning fine, but many are not, and repairing them - especially the electronics - will get harder with time. At age 54, I hope to still be shooting with these cameras for another 30 years or so. To do that I figure I will probably need several bodies of each model, just to have the proper parts to keep one or two functioning. So I am always on the lookout for good deals on F2s and FE/FE2s, and to lesser extent FM/FM2s.