There are already many solutions to the performance issue from which you can pick. You don't need to understand the C in numpy to use it for example. And I'd say it's highly unlikely that you have a use case that, if it's applicable, isn't already addressed. Like it's generally pointless to optimize language performance for code that's doing a lot of network operations, because network lag will always dwarf such optimizations.
There's so much Python code that uses numpy etc but still ends up having some hot part in Python that's nontrivial to translate to something faster. Same reason people get frustrated with the GIL.