> Why should I hire a junior who doesn’t know the what or the how.

I'm not saying you should. It's the business model that will answer that question. But the traditional wisdom was that juniors are not costly and have few obligations tying them down. And juniors don't stay junior.

And some may know the what and the how, at least technically. What they may lack may be just how to develop their skills further to be useful in a professional settings. It's easy to learn programming languages, tools, libraries and frameworks when you have a lot of free time. And they're not asking to be your protégés, you're just training them to be useful for your team.