Some developers like to bundle the Windows and Mac versions of their programs together— maybe it’s more convenient for them; I don’t know. Windows users are expected to install the Windows version, and Mac users are expected to install the Mac version. I would think that it’s less confusing to the end users if the Windows, Mac, and (if available) Linux versions were packaged and distributed separately, and most large developers do create separate installations for different operating systems. But small developers will occasionally put the Windows and Mac versions together in one compressed archive, but within two separate folders.