[{quoted}](name=Overlord Forte,realm=NA,application-id=6kFXY1kR,discussion-id=6EifGrmw,comment-id=0005,timestamp=2014-12-22T04:38:02.567+0000)
Because, much like the Reapers (mass effect), even though there is 'evidence', national leaders cannot afford to deal with 'superstition' for the most part. They need hard evidence, backed by multiple sources and people, to constitute a response. It's the most prudent, and safe way, to command a nation.
Champion wise, why individual players are so unconcerned? It's hard to say. Maybe some are, but it's not part of their agenda. Quite a few mages are probably aware of the Void, just not directly affected by it yet.
I mean, that excuse would work if there was only superstition of the Void. There are 5 creatures from the Void currently in Runeterra, and one being that has been accepted to be the Void's prophet. In Mass Effect, they had Saren to blame for the Citadel attack, but in Runeterra, there's no scape-goat.
This is a rather large plot-hole, now that the League is no longer containing all of the Void creatures.