It only makes sense because it's python. A language where style is part of the syntax, and readability is one of the things that many libraries focus on , the so called being "pythonic".
It makes sense that the reference implementation mirrors the same patterns than the language itself.
Someone else already posted this link: https://www.youtube.com/watch?v=qCGofLIzX6g&list=PLRdS-n5seL...
It explains why CPython can't improve on many things.
(edit: I'm just being polemic about your statement here. CPython is reasonably optimized within the constraints it currently has).