I don't think many 'cruise-ers' are that bothered about the sensation of being on a ship.
There's another intriguing possible explanation for that glassed-in upper deck. It could be a belated attempt by cruise ship owners/designers to reduce the risk, or opportunity, of passengers disappearing, presumed overboard and drowned. There seems to be a relatively high incidence of disappearances from cruise ships. It's very difficult to get statistics, because 1) all those concerned deny there is an issue: 2) hilarious (black-humour-wise) buck-passing goes on about whose responsibility it is to investigate such an occurrence. Take your pick from the port (nationality) of registry of the vessel, the port (ditto) the vessel had sailed from, ditto it was sailing to, the waters in which the incident might have happened, the nationality of the victim: and probably some more.
So, if you have a tiresome relative to get rid of, and can afford it, you know what to do. Unless the upper deck is glassed in, of course