I'd rather readers of such code take the (IMO minor) extra effort to consider the possibility of the worlds being different rather than bake the assumption that

I'd rather readers of such code take the (IMO minor) extra effort to consider the possibility of the worlds being different rather than bake the assumption that they're the same into even more code. That's how globals spread around your codebase, little by little, until it's very hard to refactor away from them. Better to just say no from the start. Also, if you have so many globals that passing them around as parameters / instance variables becomes truly tedious, that can be a valuable signal that the program is poorly structured. Of course, none of this matters in small codebases, as long as they stay small.