Are Graphical Artists and such considered developers?

Hello, we had a discussion at work whether if graphic designers and artists are considered developers.

Most said that they aren't. But I think it's wrong. They take an active park in the development, so why are they not considered developers?

Their argument was that developers are only those who writes code or edits UI. It seems that programmers and developers are used interchangeably and I think it's wrong. A programmer is a role in the development just like Graphical Artists is a role in development.

Am I wrong here?