Interesting thread! Two sides to every story. First, if you can't even be bothered to be civil to CC when entering the plane, then congratulations - you're officially a miserable git and I hope you enjoy negotiating your miserable way through the world.
Other side - I am never grumpy at the door, but I confess I am sometimes grumpy on the airbridge when the queue seems to be completely stuck solid. The first aim of boarding is surely to be as swift as possible. A lengthy greeting or interaction between the CC and SLF is not in anyone's interest. In the Middle East I have actually been walked to my seat (in Y) by a cabin attendant and lovely though it was it would surely impact on overall speed of access for the others.
up to the 1950's friends and relatives could board the plane to say their goodbyes
Charming, but an absolutely appalling idea if you think about it.