What are the advantages of having a redundant network?

If you look at redundant networks in nature, like the network of the veins within a leaf you may realize that redundancy creates resilience.

Often leaves are subjected to parasites or physical damage. If a vital vein is struck in a network without redundancy it would mean all tissues or nodes which it previously fed into would be effectively annihilated from the network (death). A redundant network overcomes this problem by spreading out the risk.

From a Computational standpoint this would be the same problem. Often critical layers of a network if left without connectivity would create critical failures for parts of the network which may be dependent on its activity. Such is the nature of hierarchy.