But too often, estimation is seen as:
"How long will it take?" - "2 weeks." - "That's too long, how about 1 week?"
This is not a cooperative atmosphere, but a battle of wills. This behaviour pushes people to underestimate.
"You said this would take 3 months and it's been 4. You should work evenings and weekends to meet the artificial deadline that was based on your estimate."
This sets the stakes too high and makes estimation a stressful activity.
"Why is the project late? You said it would be ready in 3 months." - "It's not my fault, the developers said 3 months."
As a manager, it's my responsibility to provide time and space (and psychological safety) for my team to estimate well.
"When will it be done?" is not the only question you can ask to help with planning. Try timeboxing. "Let's work on this for 2 weeks and see how far we get." Or asking about clarity. "How well do we understand the task?"