File is a standard default menu title. From Gnome's HIG:
The File menu contains commands that operate on the current document. It is the left-most item in the menubar because of its importance and frequency of use, and because it is a relevant menu in many applications. Historically, because most applications already had this menu, and because the distinction between closing documents and closing windows became blurred over time, the File menu has also become the standard location for Quit.
Thinking about it, Exit is operating on the current document, is it not? Preferences is usually in an "Options" menu, not File.
File is also one of Window's Standard Menu Bars and Apple's OS X provided menu items in their respective Human Interface Guidelines. That's in the guidelines of three of the largest Desktop interface producers. It is most certainly a standard, though as Apple's guidelines point out, applications that don't use files don't necessarily need to use a File menu and can rename it to be more appropriate:
In general, each command in the File menu applies to a single file (most commonly, a user-created document).
If your application is not document-based, you can rename the File menu to something more appropriate or eliminate it.