I'll make this quick with a Pros/Cons list.
Cons
-You now have to pay twice the vet bills if one of the snakes gets sick.
-You can't monitor any deification. If you find that there's some runny poop in the tank, how do you know which snake produced it?
-It just stresses them out because they are solitary critters by nature.
-Competition for resources. You'll often see BPs that are housed together laying on top of one another to get at the hot spot.
-
Two males will fight with one another. Doesn't look very fun for the snakes, does it?
-Unintentional pregnancies if you have a male and a female together.
-And the worst, cannibalism. Which mind you, has no warning signs. The only warning you get is when you go to look in on their tank one day and you wonder where your other snake went.
Pros
-Well at least I have two snakes together in one tank and that looks really cool. I am so cool. I am just the coolest person ever.
It's just not a smart thing to do and there is literally no benefit outside of a keeper getting their own ego stroked so just don't do it.