One thing that is never directly mentioned in the history of SQL is the available memory, cpu and storage at the time. When a mainframe has 192KB of core memory

One thing that is never directly mentioned in the history of SQL is the available memory, cpu and storage at the time. When a mainframe has 192KB of core memory and a 300KB/s disk transfer speed, coming up with a way to access all that data was important. The OP example of data in a text file would be okay(ish) today because you could load up the whole in memory and be done with it. Yes, we have more data, more rows, and larger records but are solving different problems with different tools and significantly more horsepower at our disposal. This is not anti-SQL, but the SQL-as-a-solution in history needs more context. With that context, those lessons may be less relevant.