Waterfall is far from perfect, but it has its place in many industries, where well customers have precisely-defined specifications. In software, people usually

Waterfall is far from perfect, but it has its place in many industries, where well customers have precisely-defined specifications. In software, people usually don't know exactly what they want, let alone be able to precisely define it. This situation lends itself perfectly for rapid-prototyping to discover what works fast... which is basically an agile approach.