Unfortunately, I think the bedspread quilt rule holds true with cruise cabins as it does hotel rooms. The sheets get changed and cleaned for each new guest, but the quilts DO NOT get cleaned or changed for each new guest. I know its disgusting, but true.
Dateline did an undercover segment on how clean is your cabin? and it was very alarming at what was found and where. I guess you have to think of it as a hotel room. It can only get cleaned so well.