Some brides don't feel comfortable without the line. They know that Aunt Susie from Michigan is going to corner them for an hour going over every minute detail of her bunnion surgery until said bride is going to forbid her new husband to feed her wedding cake.
Being gracious to Aunt Susie is part of growing up, but that doesn't mean you have to let her corner you all evening. At a reception, you need to spend some time with all of your guests. You've got to work the room so, you listen to Aunt Susie about her bunnions for 5 minutes and no longer. You give her your full attention. Don't look over her shoulder to see the persons you desperately want to visit more. Remember.. "your full attention". Then, when you have been a good listener, you cut her off if you have to and you say, "Aunt Susie, you are the sweetest dear for coming all this way to celebrate our wedding with us. We just love you to bits." Kiss her on the cheek and give her a big squeeze and grab the closest person's hand you can find for dear life. Try not to let a single soul leave without a few minutes attention from the bride. Afterall, they've taken their whole evening to be with you!
My mother knew I could never do this. And, if you can't either. Have a reception line!