It's careless development. Why think something in advance when you can fix it later. It works so well for Microsoft, Google and lately Apple. /s

The release cycle of a software speaks a lot about its quality. Move fast, break things has become the new development process.

That does not make sense for anything that exists over decades.

Do you want to be still using Windows NT, or C++ pred 2004 standard or python 2.0

We learn more and need to add to things., Some things we designed 30 years ago were a mistake should we stick with them.

You can't design everything before release for much software. Games you can or bespoke software for a business as you can define what it does, but then the business changes.