We sell c/o growlers of any beer on draft, ours and the rest, and as E wrote, bottles for carry-out are less expensive to take away.
That said, and to be honest, now that package stores have caught up, we're doing way less c/o for bottled beer than we used to, and that's okay by me. To cite just one example, Todd (Keg Liquors) has far exceeded our storage space and his selection will continue to grow; it's easier to keep a map around and point the way toward him. We always did c/o as a sort of customer service, but our real mission is draft beer and food, so it's all good. Draft and bottles push each other, and the rising tide's still lifting all the boats.