Anyhow, it doesn't matter. Software devs are the lowest cog, they don't get to extend the delivery date. All the layers above - management, marketing, sales etc need a date to work to to deliver their work, and they generate the $$$. No-one cares if the software is low quality, as long as it is delivered. Dev team can do further updates to bug fix after delivery. The end.
It takes a lot of trust and maturity and skill (from both technical and business side) to have continual value delivery instead of estimates. This is possible but not the common case.