Python use is widely diverse. Anyone wishing to contribute to that which is published to such a diverse community, all of whom expect Python to continue working for them without any regressions, has to be ready to cater to that diversity in its entirety.

Given that the speedup is modest (~10%) and the Python 3 migration caused enough pain for users, I get it though. If it was a 2x speedup it would be a different story IMO