>>24646151. Being a gang-rape-toy is hardly a paradise when you think about it.
2. Though NTR really isn't my thing, you have to remember with the centaur culture is that the women WANT the teaser males. If, say, you were away from the homeland, say, Japan, and say you were with a centaur women, with no males around, then you'd live a pure monogamous relationship.
In short: snuggle horse > rape worm.