Because we should all be Christians and believe in the one and only true God.
You are probably asking yourself why should I believe in God, it is 2020.
Well, here is your 200 IQ answer.
When you die and if you don't believe in God, you are not getting into Heaven but if you do, then he himself shall welcome you on the Heaven doors.
You are not losing anything if you believe in him but you might lose everything if you don't.