a flight deck moving at nearly 600mph is not really the place to make introductions and offer hospitality! The pilots, if they are so inclined, can make themselves at the exit door of most aeroplanes to say goodbye, and I do try and do this most flights. When you see how congested airspace is these days, even in the middle of the north atlantic, and how fast closing speeds are (about 1200 mph), I'm afraid the days of the 'office' being a 'meet and have a chat' arena are most definitely over.
C'mon Rainboe, with autopilot, TCAS and weather combined does it really matter if you are looking out of the window or not. My reactions certainly are not that good. The security reasons are obvious but otherwise there is no reason now that flight deck visits should not happen compared to 20 years ago.