I find it very amusing that Windows users all so often refer to the command line as DOS, and I've tried to figure out how we still today frequently get to read users refer to the ancient operating system.
It was in fact still called "MS-DOS prompt" back in windows 98, as shown in this little picture:
I found that even Microsoft themselves refer to the commands you use on the command line as "MS-DOS commands", so perhaps this is a primary reason? Even the producers of Windows confuse and mix the terms "command line" and "MS-DOS"...
When they launched Windows XP they no longer called it MS-DOS Prompt, it was then plain and simple "Command Prompt":
We've also seen end users in the Rockbox project refer to the interface as DOS or DOS-style, and there is really nothing what so ever in common with MS-DOS in Rockbox. It is just (by default) a basic text-style interface. It is clear that to many people, a text-based interface be it a music player or a command line window, means DOS.
People are weird.