No, I've cruised twice since reopening and left my vaccine card at home both times. They don't need it as they clear you electronically prior to travel. They don't ask you to bring it, and I've never read or heard of a single account of anyone being asked for it by
DCL. Imo it's more of a risk to bring it because you might lose it. I always keep mine safe at home. If you're worried, keep a picture of it in your phone.