Customizing ALL url structures (permalinks) – why is this not in the CORE?

Hi. In wordpress settings (and via wp-cli) you can customize permalink structure of post pages but not any other page types or custom posts. Why is this not in the CORE? IMHO, urls are the basis of any site and wordpress is used for many different types of websites, not just blogs so this blog-like hardcoded url structure is rather limiting and weird. IMHO, we should not NEED to install third party plugins for this that can be buggy, can break things and some of them are paid.