People who take their animals to show have to (or at least should be) quarantine their animals after. And most people never take their breeding animals or permanent residents to expos and only take sales animals, which a lot of people house separately than residents.

I'm heavily involved in the rat community. I've had friends who had rats die from diseases transmitted at shows.

Even if there was a show for snakes, I wouldn't participate. I'm too paranoid of disease transmission. Snakes can't be vaccinated like dogs.
I have too much invested in my animals to risk their health and wellbeing.

And as for standards. There's just way too much variation to come up with a uniform look in BPs. And what someone interprets as nice could be totally different from another's nice. For example, having a really reduced pattern can be a desirable trait. But busy patterns can look outstanding as well. So how do you determine what is the standard?

And is the show going to be judging strictly phenotype and genotype or conformation as well? How does one breed for conformation when it can take years for an animal to reach adult size. But in contrast, adult balls tend to not be as attractive as babies. And as mentioned before, stress is a huge issue in ball pythons. Judging phenotype will be best with babies. But they stress easily and can go off feed, which can be detrimental in such a young animal.

In theory, it sounds good to have a snake show. But it's not practical.