My DH uses a walker on cruises as he has severe back problems and the walker makes walking much easier for him. He doesn't use it at home, just on cruises. It's great also in that at times it's quite a hike from where the ship docks to the actual port area. If his back really bothers him, he just sits down on the seat for a couple of minutes.
I do have to say though that at tender ports, he rarely gets off the ship as it is too difficult to get on the tender with the walker. He enjoys a quiet day on the ship while almost all others are off. Sometimes, depending on the port, I stay on with him.