Or a befuddled asking of the same "Why?". Or an honestly curious asking.

Yes, there are plenty of rude replies, but sometimes it helps to assume what somebody really means is they failed to do a context switch. Exchanging more details can help turn a 'madness' into a method. Even if they were outright rude, doing this can lead to an answer that might not otherwise be given (even though that answer may be provided by someone else).