I didn't have a problem with booking through Carnival on my last cruise but the girl I spoke to knew very little when I questioned her about something. I had done my homework so I kind of knew the answer to my question but wanted to double check.
For my upcoming cruise the person I spoke with Carnival was very informative on the ships I was interested in and it helped me make my choice. I did book with a TA for my upcoming cruise and don’t expect any problems. I think it’s whatever makes you feel better.
I make my own air and hotel reservation .
I was just curious as to what a TA could do strictly cruise wise that I couldn’t do other than OBC.