The Welcome Aboard show is a cruising tradition for me. Of my 20+ cruises, I have been to 90% of them. It can be cheesy and repetitive, but I enjoy it. My husband can take it or leave it (and would probably rather leave it).
It signals the official start of my cruise. I have never seen the captain or any other officer at one. It tends to be the cruise director, fun squad, singers/dancers, an audience participation game, and a preview of the weeks activities.