As readers of this blog know, managing in the presence of uncertainty is how adults manage projects. This is called Risk Management.
And as always in order to make decisions in the presence of the uncertainties that create risk, we need to make estimates.
No estimates? No decisions based on probabilistic choices. No probabilistic choices? No understanding of the resulting risks (both epistemic and aleatory).
No understanding of the probabilistic outcomes and the statistical variances? No Adult Management of risk. (Remember Tin Lister's quote - Risk Management is How Adults Manage Projects)
So it's this simple, no estimates of the outcome, no risk management. No risk management, no adult management. No estimates means No Adult Management of the naturally occuring and probabilistic risk on all project work.
Here's another Tim Lister presentation show how estimates and estimating are part of all decision making when spending other people's money