If I had to guess it’s because of the rarity of it, combined with relatively few firm diagnoses.
I know we had it because it was diagnosed by a veterinary pathologist, but if you look through an average disease post on an average site most people don’t have the faintest clue how to figure out what’s affecting their fish. It’s the old joke about the tetra that’s bitten in half being diagnose with Ich.
Then even when people are careful, they’re usually looked at as paranoid. I remember an interview with Gianne the betta lady where she said she doesn’t touch fish tank water without gloves on, and at the time I thought that was way overkill. I likewise remember someone asking Cory about it on a stream and he said he’d never seen it and thus wasn’t overly concerned about doing things like Gianne does.
So, there you go I guess. I don’t do gloves but I also basically don’t buy fish anymore. I was super paranoid around the ones I have for about a year acting like they were contaminated, and now I’m just breeding those to maintain the population. It definitely changes how you keep fish, for sure.