Religion is the brother of mythology, pseudo-science and superstition. Someone makes it all up and before long it has passed down the generations as 'truth.' There must be many reasons why people sustain unprovable religious beliefs - childhood indoctrination is probably the most common – but the prize for the silliest reason for religious belief must surely go to the so-called 'Pascal's Wager,' a gambler's 'belief' in god, just as an insurance policy. It has got to be the most ridiculous reason of all.
It's better to 'believe', they 'reason', just in case god really does exist. Nothing is lost if he doesn't but if he does, you will get the magic key to an everlasting life of joy and bliss in Heaven. That's hardly a belief, is it? It's more like a lifestyle decision to bluff and lie your way through the Pearly. Gates. How very Christian!
Surely the all knowing, all seeing, all hearing god that you have chosen to 'believe' in for practical reasons would be able to see straight through through such a shallow ruse! A supreme ruler of the Universe that can supposedly even listen to your thoughts would immdeiately know about this deceit.
Believing somethng 'just in case it's true' is very shallow reasoning. In fact it can hardly be called a belief at all.