Plastic feels cheap and shoddy. Macbooks (and such laptops) feel premium, and I want a premium product. I don't care about the price for a device I live with and work on daily.
The weight doesn't bother me, and in fact I _prefer_ it having some body to it.
Regarding impact... my 2015MBP doesn't look a day old. It's tanked hits that would break other laptops.
I'm intensely curious about this stance. Apple popularized the aluminum case in laptops, and having owned a dozen each of aluminum and plastic/carbon fiber notebooks, aluminum is just... worse. It's heavier, more expensive, and every substantial impact is a permanent mar on the finish. Why is non-plastic so necessary? What advantage is there?