I think this post unveils a great truth that I never grasped: estimates are a political tool to decide what gets done and what doesn't get done. Thanks for putting it so nicely!
One thing that I'd like to understand then is _why_... Why doesn't management use a more direct way of saying it? Instead of asking for estimates, why don't they say: we have until date X, what can we do? Is it just some American way of being polite? I am sincerely curious :)