So developers must suffer because managers routinely make promises they can't keep?
Even developers themselves are often unable to produce good estimates. In fact, most developers tend to systematically underestimate how much time they will need for this or that task.
I have seen management to even add padding to estimate and it is still not enough in the end.
If the problem is that your manager isn't listening to your estimates, then find a new manager. Plenty of fish in the sea.
That's why I often 3x my estimates. It works great for me.
It's never a problem that I finish a project early. But when external launch plans are on the line, it can definitely be a problem to finish a project late.
Finishing a project on time is one of the things you get evaluated on in performance reviews as a software engineer. It's also up to the software engineer to provide reasonable estimates and to push back on requirements or incorrect estimates coming from higher up.