The current CPython maintainers believe that a JIT would be far too much complexity to maintain, and would drive away new contributors. I don't agree with their analysis; I would argue the bigger thing driving new contributors away is them actively doing so. People show up all the time with basic patches for things other language runtimes have been doing for 20+ years and get roasted alive for daring to suggest something as arcane as method dispatch caches. The horror!
This cements the CPython team as sort of a known "don't waste your time there" in PL research communities, distancing themselves from the people most likely and willing to help maintain their runtime.
This cements the CPython team as sort of a known "don't waste your time there" in PL research communities, distancing themselves from the people most likely and willing to help maintain their runtime.