Sorry, just got back and saw your reply. This is too big a topic to go into here and there's already plenty written on it. Sum is not a realistic use case. I

Sorry, just got back and saw your reply. This is too big a topic to go into here and there's already plenty written on it. Sum is not a realistic use case. If you're doing Javascript, maybe look at lodash/fp for ways people really use currying. I think my answer to "why" would be: if your mind is already geared to think about problems in terms of composition of functions, then currying (for example) is just one necessary and natural thing that falls out of that.