First, the probable reason for NOT having a fuel surcharge last year was that the cost increase was relatively temporary and fuel costs were fluctuating up AND down. The cruise lines probably just absorbed the costs knowing this.
Now the costs are up at record levels with no sign of dropping.
Second, the reason that they are not simply adding it to the cost of the cruise is ADVERTISING. For example, they can keep an advertised rate lower knowing that the fuel surcharge will add to the low advertised price (hook). Another example of this is how the various on-line travel sites advertise airfares and break out "taxes and fees" differently. My $250 ticket from Continental was that price UP FRONT. Other sites had tickets advertised at $98, but that was one way and did not include taxes and fees. With taxes and fees, the "cheap" ticket was close to $300 out-the-door. Cruise lines will use this same ploy.
Finally, I'm surprised that this is even an issue at this site because:
1) We all know fuel costs are rising.
2) We all like to cruise.
3) Cruise lines need to make money to stay in business.