I reckon everyone should believe in the supernatural world, be it religions, or just plain spirits.
Lets say you don't believe in them nor keep them happy, and they exist: you die, and you piss all of them off, and your afterdeath is a horrible experience.
Lets say you believe in them, and you keep them happy, and they don't eexist: you die, there is no such thing as spirits, and you DON'T become a spirit (because they don't exist), and therefore there is no such thing as an afterlife, and things will not be any different to you NOT believing in them in the first place.