I don't think it is any secret that in the long run the cruise lines wouldn't mind it most people booked direct.
There was a time when it wasn't profitable for a cruise line to even operate a call center because they didn't do enough business, but some people wanted to book direct.
But now that more people ARE booking direct the cruise line call centers are more profitable.
However, I would STILL use a travel agent for the service factor - you get more service for the same price.
It is like buying cruise insurance - you can buy it from the cruise line - or from a third party. If you buy it from the cruise line and they go out of business who pays your insurance?