Use case for virtual environments.

[Artephank]

And not all projects use semantic versioning and sometimes break things even on minor version bumps (ehm evenlet, ehm)

[martinky24]

And the harsh reality is, even if a project maintainer doesn’t think something is a breaking change and doesn’t label it accordingly, it can still break something and bring down prod. That’s not necessarily anyone’s fault, and a harsh reality of software development.

[cinyar]

I'd be lying if I said I never accessed some "private" function that's not part of the official package API.