Question: I know this might be a stupid question but why do they want to lift the curse? They can't die and can't feel pain.
Answer:As Barbossa explains, their needs and desires are no longer sated - no matter how much they drink they are still thirsty, food turns to ash in their mouth leaving them perpetually hungry, their lust is no longer satisfied no matter what they do, their flesh disappears in the moonlight, etc. And they are cursed to endure this for all eternity unless the treasure is returned. Sure, they can't die and feel no pain... but the trade-off is that they aren't able to truly live or experience any true satisfaction of any kind. The cost of their immortality is simply too great, and they don't want to endure it anymore.
Answer: As Barbossa explains, their needs and desires are no longer sated - no matter how much they drink they are still thirsty, food turns to ash in their mouth leaving them perpetually hungry, their lust is no longer satisfied no matter what they do, their flesh disappears in the moonlight, etc. And they are cursed to endure this for all eternity unless the treasure is returned. Sure, they can't die and feel no pain... but the trade-off is that they aren't able to truly live or experience any true satisfaction of any kind. The cost of their immortality is simply too great, and they don't want to endure it anymore.
TedStixon