This is precisely the issue from my perspective as well.
Most project managers I've worked with either have a desired estimate already in mind or they don't care about any of the extenuating circumstances.
On one hand, the desired estimate is often based on the knowledge that projects estimated to take more than a quarter aren't going to get a green light.
On the other hand, it's ridiculous how many projects blow through estimates when external dependencies are ignored, newly-hired engineers create a burden on the project, and de-scoped work turns out to be necessary.
Those project managers also pursue the same estimation agenda even after several projects turn out the same way.