Because he lives in the real universe where "good in life" is a fact about people rather than about the Awesomon, the fundamental particle of goodness.
The correct term is Moron, the fundamental particle of morality. Ronald Dworkin's straw man of a straw man. Well, I liked it.
Why Talk to Philosophers? Part I. by philosopher of science Wayne Myrvold.
See also Sean Carroll's own blog entry, Physicists Should Stop Saying Silly Things about Philosophy.
Sean classifies the disparaging comments physicists make about philosophy as follows: "Roughly speaking, physicists tend to have three different kinds of lazy critiques of philosophy: one that is totally dopey, one that is frustratingly annoying, and one that is deeply depressing". Specifically:
He counters each argument presented.
Personally, I am underwhelmed, since he does not address the point of view that philosophy is great at asking interesting questions but lousy at answering them. Typically, an interesting answer to a philosophical question requires first recasting it in a falsifiable form, so that is becomes a natural science question, be it physics, cognitive sciences, AI research or something else. This is locally known as hacking away at the edges. Philosophical questions don't have philosophical answers.