You make projections instead of estimates. You split the work that needs to be done into many tasks and project from past experiences. You cannot rely 100% on

You make projections instead of estimates. You split the work that needs to be done into many tasks and project from past experiences. You cannot rely 100% on any estimates either, and all you are doing by demanding estimates is creating stress and making people less productive. The meta work imposed by that in itself will make a project take more time, as everyone will be padding their estimates.