In Singlish, there’s a question that typically stresses people out and has answers varying significantly based on the interpretation of the questioner’s purpose. But at the heart of the question “why like that?”, the questioner is questioning reality. And effectively trying to pit the answerer against the reality at hand.
In fact, implicit in the question is that the answerer should not be accepting reality as it is but to do something about it. That assumption is something worth some attention and awareness. For one on the receiving end of the question, bringing to attention is assumption takes a bit of courage but immediately resolves the internal tension and cast it back on the questioner.
So the answer becomes “why not?”, or “what did you expect?” Maybe just done a bit more politely.