This is in tandem with several generations of programming language, tooling, best practices, etc. LLMs haven't suddenly increased people's productivity, improved tooling did.
Back when these tools did not exist yet, a lot of this knowledge didn't exist yet. Software now is built on the shoulders of giants. You can write a line of code and get a window in your operating system, people like Bill Gates and his generation wrote the low level graphics code and had to come up with the concept of a window first, had to invent the fundamentals of graphics programming, had to wait and interact with hardware vendors to help make it performant.
Back when these tools did not exist yet, a lot of this knowledge didn't exist yet. Software now is built on the shoulders of giants. You can write a line of code and get a window in your operating system, people like Bill Gates and his generation wrote the low level graphics code and had to come up with the concept of a window first, had to invent the fundamentals of graphics programming, had to wait and interact with hardware vendors to help make it performant.