That is an odd question, but based on the research I have done I could give you a lot of answers:
1) the potential to survive is there
2) the pain
3) it is better for the families to "disappear" rather than openly commit suicide. I think this is one of the exact attractions of cruise ships as a means of suicide. Maybe many of these people know how much it will hurt the families to know they gave up, so they choose to "disappear" and leave the suicide issue out of the equation.
By the way -- this last aspect also explains why most cruise ship suicides do not leave notes. They want the suicide without the stigma of suicide.
I could write an entire editorial right on the benefits of using a cruise ship for suicide - but if I did that I would just be providing grist for even more suicides, so I have said enough.
Just one last thing - if anybody reading this thinks the cruise industry, and people seriously considering suicide, have not already thought of everything said here you are wrong. But there is always the "compulsive suicide" the people who maybe didn't even know they planned to do it. They get drunk, depressed, and perhaps look over the side and think "I have a 50/50 chance, if I make I have proved I have something to live for."
- Well, guess what, you aren't going to make it.