The code codifies the intent and is the long-term source of truth for how your business actually operates.

>The leader of a product/company does not have to read code.

That's because he's paid a bunch of people 300k to read it and make sure it aligns with the company's objectives and interests. Part of the reason why devs are paid so much is because they're literal business administrators for some narrow slice of the company's operations. The devs are the leaders that you're referring to.

Even in multi-hundred-billion-dollar companies there are so many mission critical things that are owned by just 2 SWEs.