I also am a frequent flyer and am struggling to remember a flight when I wasn't asked for my boarding card at the aircraft door.
Another point to consider is when I have sat at the front, as I like to be on the plane early, I often watch the boarding process and usually most people at gripping their boarding card tightly to remember their seat number.
I suespect that being asked for the boarding pass therefore is a mild irritant to only a few and as regular flyer I would prefer not to be delayed by someone being on the wrong flight.
Finally called me old fashioned but it is nice to be greeted by name as you board.