Software seems to be the only area where we often try to combine designing a system with building it. Or declare that one should just start building it and the design will emerge.
Perhaps this is because in the material world, limitations of physics, materials properties and manufacturing processes are intuitively understood by non-specialists.
Building a house is a good example: a house is a composite of multiple subsystems: structural, electrical, plumbing, HVAC and so on. These subsystems won't just evolve independently to end up well-enmeshed in a coherent whole, and no future homeowner would assume such a thing and tell their contractors to just start building the house and not worry about blueprints.
Yet software has very real limitations in terms of complexity, physical resource utilization efficiency and so on, but these are not intuitively obvious to non-technologists. It is very easy to build something that appears functionally correct but is crippled in terms of scalability, maintainability, scalability, stability and so on.
So while not every detail has to be figured out and specified in advance, overall structure/architecture and how different subsystems should interact does need some forethought and definition.
