In general, I agree that people should not bring bags on board that they are unable to put into the overhead bin by themselves. There are exceptions of course. As a passenger, I will help elderly or very short people with the storage of their bags if they cannot do it or the FA won't help. However, I will not help able bodied folks store their carry-on luggage.

I was on a flight from LAX to DFW (I think last year) seated in F. Ann Coulter boarded after me and was seated in the row in front of me. She had a hulking big carry-on that she was unable to put into the overhead. She asked me to assist and I declined. She was none too happy with the rejection. She then asked an FA to help......and he also declined. Finally another passenger offered to help her. There is no reason that Ann Coulter should not be able to store her own carry-on luggage.