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.
I think a non-trivial part of why deadlines are always wrong is something akin to the Coastline Paradox [1], where the closer you are to something, the more details there are.
At some point you have to just say, "Fuck it. It's good enough" and leave it as the terrible flawed pile of crap it looks like at the detail level you're at.
Often once you step back and look at it from a customer perspective, you had just gone in too deep and they didn't need half of what you were preparing for anyway.
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.