Quoting "Matthias Klose" <doko@debian.org>:
Also the platform package manager should be the preferred way to install packages, not pip, so even a Recommends is a bit strange.
Yes, a "not-recommended" field would make sense here. As a passionate pip hater I would go for a Conflicts, which finally would make pip uninstallable :~) Next steps: get rid of gem, npm, EPT, ...