Exactly. And let's not forget that the "training" is actually new scholarship, not just learning an existing skill, so even if the PhD doesn't do anything after earning their degree, human knowledge has expanded ever so slightly thanks to their years of effort.

This diagram neatly sums it up. http://matt.might.net/articles/phd-school-in-pictures

It's the equivalent of learning to code, learning a modern library or framework and its best practices, and then adding a bug fix or new feature.