>You don't have to believe that every single employee at a company is productive or necessary to understand that you can't saddle your remaining employees, even if you picked the "right" ones, with the remaining workload.

This is exactly the problem with this thinking. A lot of people don't contribute as much as the top contributors, but if you remove them, suddenly the most productive people have to do their normal jobs plus all these other peoples' too. Then they're going to feel overworked and look for a better job elsewhere.