@Ragman,
Some of U.S. culture does use verbal agreement with a handshake; my old and best boss did. He is japanese american and he had many chinese clients, and a handshake was it. They would often hire him for more work on other projects and recommend him/us to others. Of course, that was all preceded with lengthy discussion, and not all of their projects were that way, given the complexities of architecture, but it happened fairly often. A letter of understanding would follow, but that was fairly short, one page, max two. It was the handshake that mattered.
Alternately, the majority of our jobs, in a more ordinary business culture with more usual business circumstances had all matters nailed down at length.