Most Pet stores don't know what they are doing. I mean, what pet store is going to house the 20 imported baby ball pythons they get in their own enclosures when you can put them all in one cage and have the other 19 to stuff full of other reptiles.
Seriously, most reptiles don't enjoy each others company, there actions are purely motivated by instinct. Survival of the fittest can happen in captivity too. One snake is larger and more dominant than the other, therefore it gets all the best heating and territory, while the less fit snake gets the left overs and is less fit.