They split out core components that are built-in to Python so that they may distribute them separately thereby breaking the Python version's default tooling that is supposed to exist, in the name of "not having dev tools installed alongside non dev".
Package maintainers have made life miserable for those of us who have to then help people through that mess so that they then may use the software we have written and or maintain. We have to write our quick start guides to tell users how to get a proper working version of Python on their system because the package maintainers deem their way of deploying Python the best way to deploy it.
"Your instructions are wrong, `python3 -mvenv venv` doesn't do anything, it just errors out saying I need to install something else, but when I install that package it still doesn't work".
Packagers that insist on splitting every dependency then put the onus back on the community to support it, they don't have to deal with it.