I've seen some pretty bad bites from cohabs, along with a couple cases of cannibalism among ball pythons, that's besides the obvious issues of spreading disease, mites, adding unneeded stress to the animals, unwanted breeding. I guess I don't really see what the pros are? It's not natural or normal for them to hang out in multiples from my understanding. Only needing one cage? But if one were injured or sick you'd want to separate and have an extra cage around just in case to be prepared.