Well, I should say all additional full nodes being run, would add some more redundancy. 
When other nodes goes down and there are backup nodes, then that adds some value, right?
There are on the order of 10,000 reachable nodes. So we already have ~10,000x redundancy, adding more doesn't seem like much of a value. Also, I was mostly trying to ask about someone already running one or more nodes adding an additional one-- the additional one probably goes down if the rest due, so the addition is not much value. When other nodes goes down and there are backup nodes, then that adds some value, right? There are plenty of reasons for people to run bitcoin nodes-- better security, better privacy... but not really any gain in having a hosting party run multiple.