1. The obvious reason. To hold stuff. Carry small essentials that you would otherwise put in a clutch. Lip balm is a savior. You will be talking and smiling for a better part of the night. Your lips will be awfully dry, so it will be nice to have lip balm an arm’s length away. Put some mints in there, maybe a toothpick or small mirror. Just don’t pull a George Costanza and have a wallet the size of a sub sandwich shoved in there. People will start to talk.
2. When you don’t know what to do with your hands…put them in your pockets. Sometimes your arms just hang at your sides like a couple of salamis. Especially towards the end of a long, strenuous day of getting married and being a party animal. Stick those hands in your amazing dress pockets and bam! Done!
3. People will be so jealous of you. Not to sound vain or anything, but it is all about you. So why not send people over the edge of jealousy by wowing them even more. But don’t forget to tell everyone that compliments you on your dress, that it does indeed have these little hidden hand caves. Otherwise, it’s all for naught.