Supporting "Many" is complex: you have to worry about multiple items, the order they're in, adding and deleting.It's easier if you have just 1: you always know which one you're talking about.Even easier is 0: don't allow any.("Few" (e.g., only 3) is often more complex than "Many": the constraint may need to be managed, and the list of items must be managed against the constraint.)For example: a word processor that supports mixed fonts and styles must keep track of the varying styles and varying widths of characters. If the user can only choose one font/style for the whole document (as in Microsoft's Notepad), the system still has to manage character widths, but not the variety of styles. If there is only one fixed-width font (like an old-school text editor), the system can manage characters rather than pixels.