For some a TA is a great asset in their corner....simply because they want the TA to handle all their vacation travel plans. For others, they prefer to handle everything themselves. Either way is dependant on each persons wants and needs.
Fact... a TA can assist if there are flight issues while you are enroute to your destination
Fact... a TA can assist in hotel, rental car, shore excursions, etc....
Fact.... a TA will go to battle for you if something goes wrong during your cruise that you feel should be addresed for compensation after you retrun
Fact.... a TA is able to discuss various cruiselines and their positives and negatives to assist in finding the cruiseline that best fits your needs or lifestyle.
Fact.... a TA can assist in suggestions regarding ports of call you will be visiting
For some.... all of the above is a nice "comfort zone" and provides piece of mind and less possible stress.
Does everyone need that "comfort zone" ??? Probably not, but it is available to you at no charge by the TA.
If a TA is able to provide OBC or perks to you, and does not charge a fee for any of the above services, why would you not want to use the services of a well trained, and knowledgeable TA ?
TA's are multi faceted..... Booking direct with the cruiseline cannot provide some of the valuable assistance that a TA can.
In the end... you have to do what you are conmfortable with, and that may or may not be to use the services of a TA...... It's all a matter of choice !