Even the possibility of miss-directed luggage brings up the point about being prepared.
I travel a lot so when checking bags, I also have a carry on with at least 1 day of essentials, all valuables, and anything unique needed. On our cruises we carry on a change of casual cloths, shorts, swim suit and a couple of changes of underwear. That's not very far off from what the cruise lines recommend anyway since you luggage may not be delivered before dinner.
In 25 years of flying and 4 cruises I’ve had one bag delayed (caused by changing flights at the airport due to weather) and never lost a bag.
I wouldn’t want to live out of my carry on for 5-7 days but free laundry and the shipboard credit discussed would definitely make it doable. Besides, there’s the ports where you could pick up anything the ship stores didn’t have.
I guess it's all about how you approach the adventure of life.