I can relate. My wife didn't pack bras or underwear on our honeymoon, either.
It all started when we started dating and I asked her why she wore bras with dresses that were designed to be without them. Then she started noticing in photos of herself how tacky the exposed bra straps and bra cups looked, so she started going braless not only in dresses, but all the time. Then she suggested that it's healthier to go without panties, and I encouraged her to try. That's all it took.
She didn't wear bras or panties for the first three years of our marriage. It all came to a crashing halt when my wife got out of the car in a short skirt and no panties, but her dad was standing there and said something gross to her when he saw everything. She hasn't gone without panties since.
(Except when I reach up and pull them off around the house, but that's very tame in comparison.)