People tend to be brand-loyal on expensive things, and when the camera-systems really hit in earnest in the 60s, brand-loyalty became entrenched. So a lot of people are Nikon people, and a lot are Canon people, and a lot of them are Minolta people, and so on, much the way that there are Ford and Chevy and Toyota people now.
Most of us are willing to admit that the other guys make good, perhaps even great, cameras. But they are all designed and engineered a little differently, they all feel a little different in our hands, the lenses and accessories are different, and it takes a fair amount of gray-matter to keep all the models and upgrades straight for a single manufacturer, must less several. So we tend to pick a brand we like and stick with it.
I'm a Canon guy, so I have a lot of Canon stuff and I know a fair amount about them. But I did pick up this Nikon Nikkormat FTN anyway, and its 50mm Nikkor AI lens, as a curiosity. It's a nice camera, but it's definitely a Montague in a Capulet home.
The Nikkormats were Nikon's mid-tier camera line, competing with the Canon F-series and the Minolta srT series. Unlike its big-brother, the Nikon F, a Nikkormat did not have the interchangable prisms, or the winders or motor drives or backs. But it got to use the famous Nikkor lenses, and that was more than enough.
Another all-metal, all manual camera, it looks and feels like a tank. Pros used them as back-up cameras, and students knocked them around. They take a beating and keep ticking. That's the nice thing about these all-metal wonders from the 60s and 70s, they'll be running long after the electronic marvels have electronically died.
Camera manual: Orphan Cameras.com