[cntainer]

The people getting paid salaries to have a bird's eye view and veto power over those kinds of changes that could screw with my deliverable should be the ones knowledgeable and accountable for that estimate

But they are accountable to their stakeholders (clients, upper management, etc). They take your estimate and many others from other people in the team and work those into a delivery plan.

A good manager will know how to manage risks and remove blockers in a way that gives a developer the best chance to work within the estimate. A bad manager will usually have no plan and put all the blame on the developers if things go awry.

[Zetice]

Agile frameworks often remove the developer as much as possible from the time estimation effort, instead relying on past performance, and attempting instead to have the developer focus on breaking work up evenly.

[cntainer]

Sure, this helps by removing some of the bias, if done right. But many times devs end up perverting the original intent of the framework.

Eg: I've seen many scrum teams transforming story ponts into days or vice versa missing the actual purpose.