When a team is functioning well, deadlines don't matter because of course everyone wants to get the job done, to impress their teammates and feel like they're contributing.

When a team is not functioning well, all the estimation in the world won't fix it. It'll probably just make it worse. And if management decides to use estimates as a measuring stick, engineers are right to dig in, over-estimate, and push back on management in the exact same way they're being pushed by management.