Academia & Industry: Pursuits of Novelty vs. Finessing through Reinventing-the-Wheel

Over the past few months, I came across a few PhD students who encountered ongoing projects in the industry and asked,

“This problem has been solved. Why is XXX reinventing the wheel?”

A few years ago, I would have had similar thoughts. After working for a while in the industry where I no longer do pure research, my perspective has changed.

What is “solved”?