Hoot51

I don't think he was talking about the features of credit card vs cash. It was the fact you would assume he/she has a low limit just because they want to load an account with cash in advance. There are plenty of reasons for loading an account with cash instead of just low limit. (e.i. great for budgeting or knowing how much you spent to gauge how you'll move forward with the remainder of the cruise) I don't think it's because you "don't understand" rather "do not want to understand" It could have been worded or phrases differently. 
I read it the same way as @Jim82Mac
We're all on the same team here, no worries @Atlantix2000

I usually bring a certain amount of cash on me and on one of the times where I find the desk quiet I'll pay towards my bill. I've done it every cruise without an issue. Whatever my cash did not cover my credit card, already on file, did.

Exactly the way we approach it.

Yes, you can add cash once on board through guest services. Any balance left on your account through the last day of the cruise will go towards the credit card linked to your account.
You could however, also go to guest services on the last night and pay off your balance with any remaining cash you might have or put it on a different card. Otherwise at like 3 or 4 am it charges your card if I recall. 
Wow, this is extremely unnecessary! Very rude and uncalled for.