Originally Posted by YYCguy

As a flight attendant, I can tell you that it's important for the FA to see the boarding passes as sometimes there are more than one flight going out to the same destination at adjacent gates or within mere minutes of one another (while one may be the non stop and the other being a one stop flight). So viewing the boarding pass is really to double check the flight number and destination and not so much for the seat. It has happened more than once when the FA at the main cabin door hasn't checked the boarding passes and the count is wrong, because someone got on the wrong plane. I also greet people coming on the aircraft with a smile and friendly greeting and gently ask for the boarding pass if not already presented to me!