In Pirates of Caribbean: The Curse of the Black Pearl, while carrying one of the Aztec medallion, why were Will and Elizabeth not cursed in the same way others were?
The curse is more than just about stealing the coins. The motivations of the thief are involved.
Will and Elizabeth do not steal the gold out of greed like Barbossa's crew or Jack.
From the script
BARBOSSA (CONT'D): So the priest, with his dying breath, called on the power of the blood of his people, and put on the gold a curse. If anyone took so much as a single piece, as he was compelled by greed, by greed he would be consumed
It wasn't just carrying the coins that caused the curse, it was the act of stealing it from the Aztec treasure chest.
When Jack Sparrow wanted to be cursed, he lifted a coin out of the chest, thereby stealing it and being cursed.
It was in the films made clear a few times that those that GOT the gold by any means were not cursed. Only those that stole them from the chest got cursed (which is why Sparrow despite him not doing it out of greed got cursed when he took the coin from the chest).