Separating interfaces from implementations is ALWAYS good design. If I understand correctly, a pure virtual interface avoids inline functions. And there can be

Separating interfaces from implementations is ALWAYS good design. If I understand correctly, a pure virtual interface avoids inline functions. And there can be a lot of one-liner inline functions in a large project. So there's a diference between standard good-design and this yet-another-thing-that-became-a-pattern.