All MY pilots and aircrew members got a major kick when I had to “lovingly” see them off, although it would never have occurred to me to pat them on their helmets...
They knew that I knew what their actual expected mission attrition rates were.
They also knew I had a fear of heights.
Nothing beats pouring a playfull fighter pilot into an F-15, while both of us are in full chemical gear, and watching his face change when I tell him what his new mission is ...LOL!
Naw...I’m USAF, although I did some time in a Navy squadron. It actually has to do with how hard it is to get to the harness buckles. In aircraft where it is pretty easy, the pilot (or WSO) does it himself. In others, the crew chief assists.
Personally, I always pulled the buckles first (to make sure no one had cut them then re-inserted them...something that bought a bitter crew chief in F-4s some jail time), and left enough slack that I could get to them.