To get a rough idea of what work can be done in the next X weeks, so that the business can forecast.
The wisdom comes in knowing things can change and it's just an estimate. The process of estimating is quite good as it requires finding out a lot more about how you will solve something, and planning things in advance.
Forecast to what purpose? What is the business actually trying to achieve for which they believe, maybe wrongly, they need accurate software estimates?
