There is nothing inviting about someone saying "don't do that" to you. If you actually want to understand a beginner's intentions, you're a lot better off asking them what their goal is.

In my experience mentoring new developers, it's much more helpful to ask "what is your goal?" instead of "don't do that."

No; the correct answer in that case is "Why are you trying to do that?"

That's what pedants do.

When I was a kid learning line number BASIC, adults answered my questions knowing that I'd figure out The Right Way before anyone hired me to write the code for radiation treatment devices.

The tech community's obsession with "The Five Why's" is toxic. When asking questions, you always have to first prove that you deserve an answer. It becomes a process of trying to anticipate any potential reason someone might have to argue "You're doing it wrong" - and preempt that. You can't just ask a question: you have to both ask and justify.

Mostly I just don't bother, and I suspect that I'm not alone. And I have a degree and industry experience. It must be incredibly frustrating and discouraging for beginners.

Dunno. If someone asked me how to get the bytes of a string, I would ask why. Not because theres The Right Way to do things, but because they might be doing things The Hard Way.

A why can reduce the amount of code written by 100%.

Sure, but when someone is first learning, frequently the true answer to "why are you doing that" is "to see what happens" (even if they have some flimsy justification within their pet-project at the time.) Giving them the answer lets them go back to experimenting so they can see, for themselves, why the path they're heading down might not be such a good idea. Formative experiences and such.

Yeah, that's a fine answer. But they might just not know of the other way to do things.

Like, in Java, for a long time I didn't know there was an output stream that you could write a string directly, so I was always getting the bytes to write it. I wouldn't call that a formative experience.