My friend Monica, who's an interior designer, turned me on to this quotation by world renown furnishing designer Florence Knoll.
It's a simple, lasting truism that applies to all fields of design, in my estimation. It's also a reminder of the distinction between art, which is often created for the purpose of self-expression, decoration, illustrating the written word, propaganda or other forms of socio-political reflections, versus design, which must embrace functionality—that functionality which, if well executed, is useful to the user, and hence, good business.
But then again, innovative graphic designer Stefan Sagmeister may not agree... See this brief Sagmeister interview for a contrasting point: Graphic design, while often employed for a utilitarian purpose, sometimes straddles the world of simple expression.