It's solving a completely different problem, Pyenv is entirely about managing versions of Python itself, nothing to do with venvs or packages.

Say you need to have a venv but for a specific Python version:

  pyenv install 3.8.5
  pyenv shell 3.8.5
  python -m venv env
  source env/bin/activate

Now your venv is for 3.8.5, and running `source env/bin/activate` will always activate that version within the environment.