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.