As a frequent flyer in all classes it's definitely the numpties who carry giant bags and cases then fill up the overhead bins that cause this need to board early. Sometimes it can get very difficult fighting over bin space and I really object to people rearranging my belongings, especially if they're not even from the same row or adjacent seats. I do wonder why airlines don't police the baggage more strictly as I often see people bring on more than is strictly allowed.
airsmiles