Emily's answer sort of covered the "It's not as simple as it might seem" aspect, whereby the bit that's genuinely tricky is to provide access to the system pip(/setuptools/wheel) without providing accessing to the system site packages in general.

If the latter is actually considered desirable, then the most suitable venv configuration is likely to be:

    python3 -m venv --system-site-packages --without-pip

as that will give you a fresh venv to install your own additions into, but use the system pip package by default, rather than automatically bootstrapping a venv specific instance of it.

We don't currently discuss that kind of hybrid configuration in the docs, so it may be appropriate to reopen this as a docs issue, and add a new "How do I use system level Python packages from a virtual environment?" question to https://docs.python.org/3/installing/#how-do-i