Easy, it shows what is achievable if there is a high bar for quality in every single line of code that gets commited, reviewed and merged, regardless of the programming language.

However in the days of race to bottom, offshoring for penies, and now LLM powered code generation, this is a quality most companies won't care unless there is liability in place.

Curl and SQLite are my favourite examples of properly engineered, rigourously tested _anything_. It's really philosophical - those projects' contribution requirements demand such rigor, and the maintainers stand by that demand. A non-load-bearing document (not project code) is what makes that possible - very reminiscent of Einstein's thought experiments leading to tangible projects such as GPS or Descartes's belief that all problems can be solved through rational thinking.