CV2 is kinda weird. I guess they didn't want more variables?
-Hearts are the source of ammunition for subweapons such as the sacred flame, golden dagger, and diamond.
-Hearts are also the method of currency from shopkeepers in the game.
-Lastly, Hearts are also your experience points. If you kill an enemy and it doesn't drop a heart to collect, you also don't get its experience value in order to level up. It's really messed up if you are having an unlucky streak where enemies won't cough up the goods (always beat up gargoyles in the mansions, where time stands still).
It's messed up that they didn't give you an XP value upon defeat, for enemies, instead of the 'heart'. It's also messed up that they didn't keep a money value and had you pick up money bags instead of hearts from enemies, randomly.
This is what I would fix if it were up to me to do a remake.