... I'm still doing what the military trained me to do. I was in the military VIP community for many years with domestic and overseas postings. I served my final six years at Andrews AFB. When I was in a military uniform no senior officer, politician, or foreign dignitary would have dreamed of offering me a gratuity. They respected me as the professional pilot and military officer that I was. I have never expected that to be any different in my civilian uniform.
On another level, at two of my subsequent positions the company Ops Manuals have specifically prohibited the acceptance of gratuities.
On a personal level, I consider myself to be a professional just as an airline captain is or as is a doctor or a lawyer. I would never consider trying to push an envelope with a tip enclosed under the reinforced cockpit door for the 777 captain who had just given me a smooth flight to Paris. Nor would I attempt to slip a Benjamin into the hand of a cruise ship captain at the completion of a particularly nice Caribbean cruise. I have also never considered tipping my doctor for a good surgical procedure or my dentist for a nice cap or my lawyer for executing a legal document professionally. I think they would be insulted.