I get mine for free. And as long as I pay the balance on time there are no costs at all. It's really just convinent. I get a few bonuses, too. Like 15% off a specific car rental (I don't drive) and some points that I can redeem, but so far I never even bothered with any of it.
But paying online is just so much easier with a CC. I don't get the hate.
If we don't know what gravity does in this other universe, than talking about variable gravity would pointless.