I sort of equate using a ta, to having travel insurance. I sure as heck don't want to use the insurance,but knowing I have it, is peace of mind..
A ta is the same, If there are any bumps, knowing I have an advocate in my corner, to help, is peace of mind.
The person who makes your reservation over the phone from a cruise line, would be no help at all, to anyone. What services do they do for you, other than your booking?
But like anything in life..it's different strokes