Inter-team dependencies. Marketing pushes. Customer commitments. New sales dependent on certain features. Building features to increase TAM. Partner commitments for interoperability / joint deployments. Even presentations of your roadmap to customers and prospects to get them bought into your vision of where the product is going.
There's tons of things that require broadly knowing when X is going to be done beyond capacity issues.
The above are reasons a business needs estimates / rough delivery timelines. I'm not sure how my discussion of the value of estimates is relevant to the quality of them.
There's tons of things that require broadly knowing when X is going to be done beyond capacity issues.