Same reason people believe in religions. They feel a need to invent a simple, digestible fable to explain what they don't understand.
It's basically self-medication; the use of invented self-delusions to keep their fears of things they can't otherwise explain at bay.
People don't like fear - so they palliate it using talismans (garlic to keep the vampires away, rain/weather gods to prevent droughts an crop failures, imaginary deities to save them from the stark pain of knowledge of impending death and destruction, prayer beads, holy water, praying towards Mecca, feng shui, betting on black when the roulette wheel has just spun 15 red numbers in a row, crossing themselves before going into battle, rain dances, etc.)
Irrational beliefs are the balm for the fears of the inexplicable or simply nott understood phenomena.
I'd recommend a read of "The God Part of the Brain" to understand in part the biological basis for why some people are more susceptible to seeking and accepting irrationality than others.
This is why highly religious people are often the best marks for affinity fraud. LOCH was a great example of this. Creflo Dollar is another.
