"Silly, indeed. There are even pilots who have demanded Active Noise Reduction headsets and still fly around with an ear uncovered."
Not so silly when you've read the reports on noise reduction headsets.
Airline crews are reporting that they're not hearing aural warnings (e.g TCAS) as a result of wearing them . I know of at least one airline which has instructed their crews not to wear them below a certain altitude. (Note: On the Boeings I work on, most aural warnings are not fed into the headsets).
Also, crews have reported feeling dizzy when wearing these headsets on one ear only. Not 100% sure, but I think it's called "positional vertigo".
Regards.
Q.