See the History section of https://en.wikipedia.org/wiki/OpenJDK?wprov=sfla1

On the other hand, I use gcc, clang, and MSVC++ on a regular basis. But... I think the reason I care about multiple C++ compilers is mostly because there’s no “one compiler that is ergonomic to use everywhere” and I end up writing better code because of it (eg gcc warning about something clang doesn’t care about).

For Python, I mostly just care that it Just Works everywhere (modulo compiler setup for building C modules)

I'm glad that pypy exists because it forces cpython to do something about performance, but for python overall it's a pretty niche tool.

Not to mention the terrible tooling to make multiple deployment targets possible (webpack, polyfills and whatnot)