I like AR's comments - first about using them as transportation to get someplace. I think this makes complete sense - not only do you get a nice cruise but you also end up someplace special. Often the cruise across the Atlantic (for example) costs the same as an air ticket, but you get 10-12 days of cruising out of it and hopefully some nice ports of call.
I also like what he said about "cheap skates" while I do not know this to be true (I have crossed the Atlantic five times, but four times I was working and once as a passenger I was on Queen Mary 2, which in my book is "the only way to cross.") it certainly makes sense. You would accrue a lot of cruise points, especially now that most cruise lines have gone to a "days onboard" counting system rather than a "number of cruises" counting system.
I have certainly heard stories about such people, though, so I assume there is truth to the concept.
But I don't generally judge a cruise based upon my fellow non-familial passengers as much as I base it on my personal experience and interaction with the staff, dining and entertainment.