Personally, I think anyone who is not well traveled should always use a travel agent.
Unfortunately, this "world of the internet" has created yet another problem of the "less traveled" just popping onto the Internet and booking a cruise directly with any cruise line without the proper information to make a truly informed decision.
They don't know about things like the importance of travel insurance, cabin selection, that ports can be missed for a variety of reasons etc.
These are the areas where a good Travel Agent can actually save Carnival a lot of future headaches.
Because the more informed a cruiser is, the less likely they will have problems. And IF they have problems, the more informed they are, the better they handle any issues that arise.