I've done this with many of my clothes. For one thing, it can help keep a pocket carried gun in the position it's supposed to be. It also can keep the grip from peeking out into view.
What would be nice is to have a bit more natural drape occurring around a pocket carried gun. I have yet to find a tailor that can make that happen nicely. The only real option seems to be larger cargo-style pockets with plenty of room.