Skipness,
There are valid reasons for checking the boarding cards, whether you think they're valid or not. No need to get so
about it.
Sometimes aircraft park at airbridges, which means your boarding card is checked twice in 10 yards. Sometimes the aircraft is parked on a stand where passengers have to walk across the tarmac, often several aircraft boarding around the same time.
There has to be a standard for each airline, as I'm sure you and others would be even more confused if an airline changed boarding card policy depending on where it was parked.
Also, please remember that Cabin Crew don't make the rules (nor do Pilots), we just implement them, because it's part of our job.
Gg