because you have to invest thousands of bucks into a system that locks you in with compatibility, and switching brands is very expensive. So all the fanboy toxicity you find anywhere else gets extra intense because people really don't want to admit they picked the wrong horse, because if they do it'll cost them a big wad of cash.
This also incentivizes the companies themselves to nurture and cater to loyal fans. Companies that treat everything as disposable, like Sony, fail at earning the decades-long loyalty that can be had.
It probably doesn't help that the whole camera industry is now shrinking and financially weak and many companies are in a frail state, because the cameras themselves improved so fast that they've run out of ways to make next year's model better than last year's, so most people aren't replacing the old cameras they've got. (Mine is from 2013.) So people are worried they may have bought into a brand that not only might turn out not as good, but might not even survive. All of this anxiety can help drive additional toxicity to compensate.
So I'm not surprised that cameras are where this comes out.