Housing more then one snake!

[Tsubaki]

There is a small risk of cannibalism, males can get into fights. Males can harass females, the presence of another snake could be a stress-factor. Feeding time gets harder, you can not feed them both in the enclosure. You will have to move a snake who has just eaten, which is not beneficial. If one gets sick the other(s) might too, also if you find a regurge or a weird stool or anything similar you will not know which animal it is from. I'm sure i can think of more reasons, but there are plenty reasons not to do this.