> I have a rising suspicion that some game companies with fluid ethics do this

Occam's razor says that tooling, or developers, just aren't great at shaking unreferenced content from production builds.

I'm not a game developer, but its common to still ship unused code or css in websites, just because someone forgets to remove it, or its hard to tell if it's still used. I could only imagine this is more of a problem in more complicated game dev, especially when time to focus on non-functional requirements like that can be hard to come by.