As a result, project managers are inhibited. They either refuse to estimate or wildly inflate their estimates to make sure they are not blamed for overruns or late deliveries. 

Of course there is hope.  As any well trained PM knows estimates require assumptions and assumptions imply risk.  Multiple assumptions to create alternative scenarios enable ranges of estimates. Estimates, when one is far in time from the actual work, require more assumptions and a greater number of scenarios than close-in estimates.  Uncertainty is greater when the work to be done is farther into the future.  Ranges can and should be wide.

But, that is being rational and expecting others to be rational and knowledgeable about project estimating. The reality is that rationality is far from guaranteed when it comes to projects. Often, people in power want what they want when they want it and people who are not in power do not speak up and confront those who are in power.

A project manager has the responsibility to be courageous and to educate others regarding the realities of project estimates. 

The only certainty is that there is no certainty about most future events, and the ones we can be certain of are not particularly pleasant. It is a project manger's job to make things happen. To do so, requires that we paint a reasonably realistic picture of the way things are likely to unfold and then use that vision as a guide.  We must be ready to adjust the vision and manage expectations even if that means admitting that our estimates were wrong.

When we are faced with irrational clients and managers, all we can do is try our best to get them to base decisions on facts and reasonable probabilities. If that doesn't work then we either pass on the project or do our best to get things done as effectively as possible, expecting the blame if they don't.

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