[NotGMan]

In many project it's impossible to know the requirements up front, or they are very vagues.

Business requirements != programming requirements/features.

Very often both the business requirements and programming requirements change a lot since unless you have already written this one thing, in the exact form that you are making it now, you will NEVER get it right the first time.

[sfn42]

The problem is people don't adapt properly. If the business requirements change so much that it invalidates your previous work then you need to re-do the work. But in reality people just duct tape a bunch of workarounds together and you end up with a frankensystem that doesn't do anything right.

It is possible to build systems that can adapt to change, by decoupling and avoiding cross cutting concerns etc you can make a lot of big sweeping changes quite easily in a well designed system. It's just that most developers are bad at software development, they make a horrible mess and then they just keep making it worse while blaming deadlines and management etc.

[mkesper]

You are both right and that's why so many projects are over budget or even fail miserably.