Software development is microeconomics. Microeconomics is about making decisions - choices - based on knowing something about cost, schedule, and techncial impacts from that decision. In the microeconomics paradigm, this information is part of the normal business process.
This is why when there is conjecture that you can make decisions in the absence of estimating the impacts of that decision, it ignores the principles of business. Or the notion that when numbers are flying around in an organization they lay the seeds for dysfunction, we need to stop and think about how business actually works. Money is used to produce value which is then exchanged for more money. No business will survivie for long in the absence of knowing about the numbers contained in the balance sheet and general ledger.
This book should be mandatory reading anyone thinking about making improvements in what they see as dysfunctions in their work environment. No need to run off and start inventing new untested ideas, they're right here for the using. With this knowledge comes the understanding about why estimates are needed to make decisions. In the microeconomics paradigm, making a choice is about opportunity cost. What will it cost me to NOT do something. The set of choices that can be acted on given their economic behaviour. Value produced from the invested cost. Opportunities created from the cost of development. And other trade space discussions.
To make those decisions with any level of confidence, information is needed. This information is almost always about the future - return on investment, opportunity, risk reduction strategies. That information is almost always probabilistically driven by an underlying statistical process. This is the core motivation for learning to estimate - to make decisions about the future that are most advantageous for the invested cost.
That's the purpose of estimates, to support business decisions.
This decision making processes is the basis of Governance which is the structure, oversight, and management process that ensures delivery of the needed benefits of IT in a controlled way to enhance the long term sustainable success of the enterprise.