Is avoiding hell not in one's self-interest?
Not if you're an atheist and "see no evidence" of Hell, as they "see no evidence" of God.
Avoiding monsters under the bed is often accomplished for children via a goodnight kiss.
Avoiding other imaginary terrors can be achieved via learning about how the natural world actually works--it does so without ghosts, demons, spirits, gods, faeries, prayers, rituals, etc.
Whether the Universe can work without Pixies, I am not so sure. Pixies are a good explanation for why airplanes do not fall out of the sky. Who needs all this aerodynamics nonsense?
If one does not believe that hell exists, then there's no issue of self-interest involved.
It's like one of those spam e-mails telling you to click on a link to avoid having your eBay account suspended. If you don't think that the guy who sent he e-mail is really from eBay security, you have no interest in following the directions.