You're right. The lock on the box is primarily to keep children out. Since you don't have any, all you really need is a cabinet that organizes the guns and keeps the long guns from falling over on the ground or knocking each other, and has some method of storing the handguns so they're not just in a pile or end up under other clutter.
To give you another perspective, I remember shopping for a safe, a Liberty safe. I was at a local hardware store that stocks and sells them. There was one model there that caught my interest for its size and features. Another customer saw me looking at it and said, "That's a nice safe. I've got one just like it." I said it is nice but I wasn't sure I needed the fancy champagne paint job. He explained that it's what you want if you have it in the middle of your living room.
I realized that I just saw a safe as a utility cabinet for storing guns that I have no intention of showing or displaying because they're just tools to me. But many people will prominently display their safe in their living room, their garage, or wherever they have their "man-cave." The champagne gloss paint might not be everyone's taste, but even a "textured black" can be an aesthetic choice for the connoisseur of "black" guns. I realized that I've seen numerous Youtube videos where people display their guns safes in the background, or even stand in front of them to show off some of the contents. I get it. There's a social aspect to gun storage for some people. The open or glass-front gun case or wall-mount racks now carry a stigma of irresponsible gun-ownership. The gypsum-stiffened steel boxes with fancy paint and chrome knobs are in fashion.
To organize guns, I bolted a louvered steel panel designed for mounting Akro bins to the back of the cabinet. Long guns rest in the cradles, and handguns can go in deep Akro bins. If I needed to dedicate more space to storing guns, I would get Sandusky Lee cabinets. The "wardrobe" cabinets would be ideal for storing long guns or Akro bins with handguns. They also have cabinets with shelves. With a shelf-liner or a wire pistol holder or rack, they would work well for handguns and ammo.