If you wanted to sell a product to someone who didn’t know any better, wouldn’t lying help? In the days before science, miracle cures were sold to naive buyers. We now have a name for such things. Pseudoscience.
When you get to heaven you don’t just get happiness, you get eternal and perfect happiness. You’re also told of the terrible things that will happen to you if you don’t want these gifts. Hell is worse than anything you could ever imagine; as if what you had already imagined wasn’t enough. It will be infinite torture and misery, not just the normal kind.