I don’t have Silverblue-specific experiences, but in the Workstation, it is intended to install pip independently with dnf install pip and then you can use it independently with, e.g., pip install cryptography. Then, modules will be available in the Python interpreter. But it won’t be installed by default, and as far as I remember, this has never been different. Btw, many Python modules are independently available in the Fedora repo, not depending on pip (e.g., cryptography as python3-cryptography)
The main motivation to limit packages in an installation media is the size of the installation media. Your use case may require pip, and so you may want pip to be installed by default, but given that it’s easily installable from the repositories, it does not need to be included in the default installation media. By default, the Python interpreter is included in the installation image because a number of tools require it (dnf for example).