Just to add another reason, and the main reason, I used a TA for my wedding (though I had never used one before).
I travel for work A LOT, so I often get a lot of travel questions from my friends and family. I really did not want to deal with all of our guests contacting Paul and I with questions regarding their travel to our wedding. It may sound bad, but I just didn't want to deal with it! It was so nice that they could contact Tammy, and she could help them and guide them (thanks, Tammy!). And if/when last minute problems came up, my guests didn't have to try to track me down, and my wedding week vacation wasn't interrupted.