To prevent broken internal links in case you change the permalink structure in WordPress, a simple internal link shortcode can be used. Normally it’s best to avoid changing the permalink structure, but if you really have to, internal links in posts or pages would point to non-existent pages.
If instead a shortcode is used each time you link to an internal page or post, a future change of permalink structure would mean that you wouldn’t have to manually change the link URL of each internal link.