It's fascinating to watch first hand, management's inability to properly estimate project timelines. I think it's from a lack of really digging in and solving the thousands of tiny problems that eventually add up to solving whatever larger problem it is the general organization was trying to solve originally.

Instead, I've seen mostly attacking a problem head on which involves a really inordinate about of planning, more planning, some execution, and then more planning. Planning so much, that timelines must be altered to make room for more planning.

That's been my experience though.

I believe the desire to blow through timelines planning instead of executing, is born out of fear and what I call the sensation of movement. Fear because management doesn't want to mess up and miss something important. The sensation of movement causes management to incorrectly perceive work is being done.

At the end of all of this, nothing is done because no one has done any of the work to accomplish it, they've only been planning.