I fly jetblue several times a month and I think that part of the issue comes when some gate agents board the plane by letting too many rows on at once. If they only boarded 5 or 10 rows at a time like some of them do, it seems to go smoother. Also, I do see some flight attendants that do as you do and have customers hold their jackets etc and that does help. Not all attendants do it and it should be company policy to do it, and would be easier to police if only 5 rows are boarded at a time...