Really? On what evidence, exactly, do you base that assertion? I'd guess that those who make a considered choice not to use sanitizer - particularly on the reasoning that our over-sanitized world is not in the long-term best interests of our immune systems - are exactly the same people who are most likely to realize that allowing our immune systems to develop does occasionally involve being sick.
I'm in the "no thank you to hand sanitizer" camp, preferring soap and water. Incidentally, the CDC agrees with me:
http://www.cdc.gov/nceh/vsp/pub/handwashing/handwashingtips.htm.
That said, if I'm the cruise line, and I'm facing a large number of people who probably
won't wash their hands regularly, but
might be induced to use sanitizer - I can see why they offer it, on the argument that it's better than nothing. Still, I just wish that staff was trained to recognize a polite "no thank you, I've just washed my hands" as a reasonable alternative. On my recent cruise I gave up declining after the first couple of days. I ended up just accepting the wipes and immediately discarding them. I hated to create the extra garbage, but I got tired of trying to explain that "no, really, I
just washed my hands".