Are religious rules more for making the present better, or to get into heaven?

[The Mikado]

It 100% depends on the faith tradition and on which specific rule you mean.

For example, the Prophet Isaiah makes a strong case that fasting is supposed to help you sympathize with the poor, who go hungry not by choice but by necessity. Isaiah's take is not the only one on the table, though.

[The Mikado]

Just thought I'd give a different perspective, really quickly...Moses in Deuteronomy has a case that the answer is neither to make the world a better place nor a place in an afterlife that isn't recognized, but because it is the Israelites' contractual obligation to God and that there's one hell of a severance package for noncompliance.

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This answer is "you should follow religious rules because God is judging the entire community on the actions of the entire community, and if the community doesn't play ball, the severance clause on the contract is too horrific to contemplate."

[The Mikado]

God did not make those rules; nor does God actually exist.

Religious rules were designed by wealthy aristocrats to solidify their hold to power.

Which is why half of the Bible is the Prophets condemning the Kings and the narrative itself condemning basically every king except Hezekiah and Josiah as varying degrees of immoral. Even Hezekiah(!), Isaiah's golden boy, gets knocked for not destroying the high places.

Nathan condemning David for murdering Uriah the Hittite and wedding his wife, Elijah condemning Ahab and Jezebel for the seizure of Jezreel, the entire story of Saul and Samuel's brutal condemnation of him (and monarchy in general!!!)...I guess I just imagined those and they weren't actually in the text.

[The Mikado]

If you're counting the New Testament, it does have the strongest endorsement of temporal political authority in the Bible:

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Which is even more striking in its famous KJV opening line "Obey the Powers That Be." Thing is, Paul isn't speaking from the perspective of a government authority, Paul is speaking as a member of a tiny religious minority who doesn't want to invite government scrutiny or persecution and wants his flock to keep their heads down. Even that passage isn't telling you to obey the government because it's inherently good, it's telling you to stay out of trouble.