When I worked for the military the department where I worked was located in the command section. So, it was protocol to invite the hospital commander, the section chief, and our section commander. The top two usually declined, but our section commander usually attended. Of the three that were there during my time working in this area, the first and second ones always brought something or gave money if they attended, and the last one just showed up to eat.
However, the section commanders consisted of an older male colonel, an older female colonel, and a younger single male major who had just put on the rank. This young major gave me the impression that he really couldn't handle the position; he wasn't very knowledgeable about the type of work we did, and didn't seem willing to learn, and in fact about the only times I saw him were for our potlucks.