Why? Defining ethics is extremely difficult, but volunteering our intuitions via examples helps us get closer and closer to narrowing what it is exactly that we're talking about.

It's mighty hard to pin down a universal definition for "art", "love", and even "game"- and yet we use these words regularly and mostly very successfully to communicate.

Discussing "ethics" is difficult too, but I am unconvinced by arguments of the "it's obviously all subjective" variety.