'Curry' is not an ingredient. Curry is the name of an Asian dish and nothing more. The word 'Curry' has been taken out of context and used widely , but it is not to be confused from the original meaning and origin.
There are plenty of Asian foods , there is saag which is lentils, and there is Aloo Paratha which is potatoe with a buttered Chapatti , plenty! The Curry part is all just a stereotype, its not an ingredient of every Asian food and there are plenty of other foods that don't require or use it.