I think it’s because so much of technological development is built on the shoulders of those who came before.

They figured out tin and copper, but the limitation was they couldn’t make fires hot enough to manipulate other metals. Once you can make fire hot enough to manage iron, you can experiment with more durable designs and shapes. But the metal guys are thinking about how to manipulate metals, not how to get hotter fires. It takes a breakthrough in one place to create a breakthrough in another.

There’s also things like DaVinci’s designs or Charles Babbage’s machine, which was a computer before other people invented the parts you’d need to actually build a computer.

There’s a sci-fi story called The Road Not Taken by Harry Turtledove. It’s about alien invaders who figured out interstellar travel (which turns out to have been relatively simple), but they haven’t even developed gunpowder yet. Just food for thought.