I don't have any inside information, but I would guess it's because their san is so sketchy everyone rolls their own DFS and uses other chatty replication strat

I don't have any inside information, but I would guess it's because their san is so sketchy everyone rolls their own DFS and uses other chatty replication strategies, leaving the network running data and disk on the same topology. These days a lot of that traffic will take 4 hops within an AZ.