Inertia. Newton described as a body at rest tends to stay at rest and a body in motion tends to stay in motion, unless acted upon by an outside source. OK, he actually said:
Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.
But seeing as I don't understand Latin very well I thought I would translate for you. You're welcome.
"Well, that's all very fascinating, but what does this have to do with IT?" Glad you asked. You see, a project is much like a body in motion: it tends to stay in motion. Regardless of whether or not the project is required anymore or even if the target has completely changed, the project still moves forward. There are a few skeletons of this sort in my closet, that I almost ashamed to mention. (Almost, but not quite.)
Have you ever worked on a project that was headed nowhere and doing it at a break neck speed? Imagine a project where you're almost finished the design and the technology hasn't even been chosen yet. Tough to finish your design, isn't it? Image a project where business rules are changing, but the design of the project is two versions of rules behind. Not going to be that successful is it? Imagine a project where the developers are asked to work overtime. For free. And then tell them they need to work more over time because the project is behind. Imagine a project where the Project Manger gets promoted, and removed from the project, and yet his line managers are punished for the current status of the project. Imagine a project where the "technical guru" is unable to comprehend basic technology, yet insists that his technology choices are sound. Now imagine him in charge of the overall project!!!!
All of these are reasons for a project to stop. All of these are reasons for a re-assessment of the viability of the project.
But the project kept going.
Inertia kept the project going. Inertia fuelled by pride and a stubborn reluctance to say "I think we need to stop". There is no shame in stopping a project if it's headed in the wrong direction. There is no shame in saying "Things have changed since we started, let's stop and re-evaluate things before we go too far". The objective for any project should be for the benefit of the organization. Sometimes it is better for the organization to stop a project and walk away then it is to let the project continue. Understanding the long term results of proceeding is more important than finishing the project.
(By the way, the project I was referring to was with a previous employer and should not be confused with any current or previous project of Alberta Education, Alberta Advanced Education & Technology or Alberta Learning.)