There are many re-fillable lighter companies still in existence (Ronson for one) and some are quite exquisite. Zippo was successful because not only did their product work, it was also quite affordable.
Zippo also ingrained itself into the subconscious of America during the Viet Nam war. It was the lighter of choice for G.I.s and many pictures from that era show soldiers carrying or lighting up with Zippos. Also, Zippo lighters became something of a memory book for soldiers. They would inscribe their Zippos with all sorts of drawing and inscriptions. It is the art and time capsule of a generation of soldiers.