Why should I add salt to my curries?
Your experience with the curry is normal. Salt helps bring out and enhance existing flavors. This is true for everyone, as far as I know. Different people have different sensitivities, and want different amounts, but the effect is the same. Given that you thought the curry tasted better with it, I wouldn't be surprised if you should also be adding salt to other things - maybe just not as much as recipes typically call for.