One of the reasons why they like to get practically everyone's
input is, so that if the bigshots hate the paper or there is some
cockup, the blame is spread over more people. 
Also, sometimes they get "scapegoats" to write papers on subjects
they know nothing about. So the poor scapegoat has to chase the
very people who should be writing the damned paper to begin with,
for inputs.
I'm not kidding. This really happens.
