The strange idea of requirements before design, and design before construction

I continually dumb founded that other experienced and intelligent people thing that they leap into the use of a modelling tool to record concepts and analysis without being clear on the requirements or doing design. At present I am focused on modelling of enterprise - their operations, technologies and related transitions and initiatives. I always emplore people to:
1. gather the requirements (e.g. the questions they want the model to answer) BEFORE they start thinking of the design of the model
2. sketch out a rough design in some manual method (on paper, on a white board i.e. on anything but a computer modelling system) and get that design clear in their heads.
3. go about modelling.

But people presented with a modelling tool inevitably leap to 3. Some argue they implicitly know the needs (which I seldom buy) and some say they design best using computers (which I don't buy either).

I have written in other items in detail about why the way model something depends on the answers to be asked of the model. Which I won't recap on here.

AN ANALOGY FROM MY PAST
A CAD system, and in fact architectural drawing themselves, are models of a proposed or existing reality. They are way of communicating and analysing reality.

Once in my distant past after leaving Architecture school I specialised in CAD systems for architects. After a decade of using them (and at that stage I was as proficient as anyone in the world) with them them I became more and more convinced that in the vast majority of cases the use of these tools impairs the cognitive processes associated with conceptual design.

The conceptual design was better done on the back of an envelope, scratched in the sand of modelled roughly from wood and clay. I think this is for deep seated reasons to do with human cognitive processes and design. I think it has to do with issues of gestalt and post cognitive dissonance and the tendency for electronic tools to require greater precision (dimensional, semantic etc.) than should exist at the early stages of design - i.e. where it is better to leave some things loose, woolly, undefined/less defined.

This is not to say that they should not be used - but they should use to elaborate a design (not conceive one).