I'd argue precisely the opposite.
First, let's dispense with the OFFICIAL theological beliefs of most Christian denominations in the US regarding salvation through faith rather than good works and whatnot; the reality at a gut level of most rank-and-file believers in this country regardless of the "official" theology of their particular denomination is a belief that they will be rewarded for doing good works by reaching heaven and punished by bad deeds with hell, which are cause-and-effect consequences, albeit entirely unprovable post-death ones.
If anything I'd argue an atheist or agnostic who is a deeply moral and ethical person in his actions is more impressive than a religious person who is equally deeply moral and ethical person in their actions but is doing so because they're expecting a post-death reward or avoiding a post-death punishment.
Of course this will be dodged by people living in a fantasyland, to make themselves comfortable, that atheists and agnostics are incapable of being moral and ethical people.
If anything I'd argue an atheist or agnostic who is a deeply moral and ethical person in his actions is more impressive than a religious person who is equally deeply moral and ethical person in their actions but is doing so because they're expecting a post-death reward or avoiding a post-death punishment.
Impressive to you. But maybe not to God ;-) Which is precisely the point many Christians would make; but not all religious people.
But your last sentence interests me. Why are you assuming so many religious people are motivated by fear of punishment or for rewards? King David (try reading the Psalms) talks as if he were motivated by loyalty to God and love of God; you can find similar sentiments in many New Testament writings...
Full Disclosure: ...I've not forgotten about those 72 Virginians we keep hearing about ? KABOOM! :-( Cheers!