Opinion of cruises for a vacation?

[dead0man]

My parents go on several a year and have since retirement (15ish years now I'd guess).  They love 'em, I don't understand the appeal.  They neither drink nor gamble.  They've done Europe and Egypt and several longish Pacific cruises and have been through the Panama Canal a couple of times....which all seemed fun, but mostly it's been in the Caribbean.  Seems boring to me.

but whatever <ahem> floats your boat.