But longshot bettors have it easy. Society quickly forgets all the predictions that don't come true. It remembers the one that did, and treats the prognosticator as a prophet. In social terms, predicting doom is an asymmetrical strategy, because you only have to be right once.
Which is also to say it's a cheap bet that anyone with no reputation can afford. Hence, not believing doomsayers mean what they say is a sort of societal hedge against people flooding the zone with doomsday scenarios about everything.