They want it quickly so there is no time to plan.
They want it cheaply so there are no resources to test.
They want it according to the drawing they prepared which you then later need to find places to stuff any extra features they ask for later.
They quickly get tired of answering clarifying questions about it and ask developers to "just figure it out." They also don't really care about reliability, or at least that doesn't come up much in discussions.
They insist up and down that their use case is unique and that the way they do things cannot be modified.
They have immensely complex business rules they never wrote down and can't agree on the details of as when the process was done by humans, the answer was up to the human.
So they may not ask for complexity, but that is the end outcome of everything they do ask for.