Over the years, on various liveaboard trips in British Columbia, and several trips to Cozumel, I have met many interesting people from all walks of life. Doctors, specialized surgeons, fighter pilots, teachers, dry cleaners, dive shop owners, nurses, gun shop owners, and retired people to name just a few. Every person is unique, and has a story to tell.
As Dave says above, in some places like Aldora or Scuba Club, you have space to get away from the bores, while on a live aboard you are stuck with them for the duration. On the first liveaboard I was on, there was a convenience store owner. He made one dive during the whole week, and drank the rest of the trip - his choice. There was an instructor who brought his girlfriend - she was a new diver, and he would not let her dive most of the sites - they were "too difficult" for a newbie.
When I go on a trip, it is all about the diving, and meeting new people. I still have contact with some of the people I have met, and have become very good friends with them, even though they live several provinces to the east. We are getting together again next March, for another two week adventure in Cozumel.
Divegoose