I think in most cases, understanding is the point. we don't expect students to derive general relativity before doing astrophysics. re-invention is only a tool for understanding
The flip side is even more interesting. There’s a great number of electrical engineers with significant physics backgrounds who don’t really understand how electricity actually works, but they can still solve useful problems. By understanding I mean they can describe what underlying physical phenomena reactance represents etc.
you didn't re-invent it, you learned it from a teacher and then practiced until you understood it to the required degree
If you can't derive a result in mathematics or physics from first principles you fundamentally do not understand it.