Because back in the 1980s computers booted to the BASIC command line interpreter/REPL. Nowadays, there is, more or less, no such thing. Closest similar thing most non-geeks will get to is a browser console, and while that is reasonable debugging tool for pros, it's not a similarly friendly programming tool for beginners.
In fact, you practically need to be an experienced developer even to get a modern IDE up and running. Eclipse? Xcode? Not for the faint-hearted.
Not sure about hard statistics, but I'd say it's a safe bet most new developers these days need to be shown how to get going. Beyond that, they'll naturally self-teach and bootstrap themselves, or fail out early. Because at the end of the day, no matter how you learn, your practical knowledge (meaning libraries and frameworks and tools, if not entire languages) will be functionally obsolete within two years, formal CS concepts and emacs/vim godliness notwithstanding.