In an 'ideal-project world' all projects would be completed on time and within budget. A project plan would be created up front, everyone would understand and buy into the project work, everyone would do the work, no surprises would crop up, all would go in accordance with the project plan, and the project would be completed on time and within budget.

That 'ideal-project world' rarely, if ever, exists.

How does the 'real-project world' differ from the 'ideal-project world'?

In the real-project world...

People fail to perform the Process called planning. 

People fail to perform the Process called communication.

People fail to perform other Processes.

In the real-project world People choose to do other things rather than do the Processes that cause projects to be successful.

The most-important question is, Why?

Why do People choose to do other things rather than do the Processes that cause projects to be successful?