Because nobody wants to buy a $1,300 machine that they have to futz with right out of the box.
I would think HN is the kind of place where that's exactly what people would want to do. I'm not convinced by this Chromebook either, but stock configurations / things I can change are definitely not the reason.
Even hackers appreciate a product that's awesome out of the box.
Except everyone who uses linux on a macbook pro / macbook air.