If Jewish people do not believe in Heaven and Hell, why do they follow so many rules?

I am not Jewish but I recently learned that Jewish people do not believe in Heaven or Hell (correct me if I am wrong.) Christianity, Islam, Mormonism, etc have this carrot and stick approach which keeps adherents following arduous rules for fear of hell (or purgatory) or for fear of not getting into Heaven (or the right kind of Heaven.) It can actually lead to scrupulosity in many cases, aka religious OCD.

I am wondering why Jewish people follow so many rules? Such as keeping kosher, no work on the sabbath, removal of hair for orthodox women, etc, etc…. Seems like a lot of mental energy, physical energy, time and money devoted to all of these rules without much downside if the rules are not followed, except the social downside of others judging you for not following the rules. What is the religious justification for following all of these rules? How will it help the rule follower or hurt the rule breaker? Is there a carrot and stick?