Clustering /is/ hard. There are tradeoffs to the various ways to do it, and explicit choices you have to make that have the ability to bite you in the ass later

Clustering /is/ hard. There are tradeoffs to the various ways to do it, and explicit choices you have to make that have the ability to bite you in the ass later. As one of the stated goals of Postgres is reliability and correctness, they don't want to half-ass it. That being said, there is active work on getting multi-master working well out of the box, which unfortunately didn't land in 9.4. It may make it in 9.5, but that remains to be seen.