Think of it like this. 1. How are you supposed to learn to draw something if you can't even look at it? 2. If it were as easy as looking at a photo of a face to draw it accurately... How come not everyone can do that?
Hmm. Hmm indeed.
I feel that this is one of the biggest misconceptions among (mostly) inexperienced artists - that it should somehow be cheating to study the subject of what you're drawing. But following that logic, if just looking at another person would be enough to make photorealistic paintings, how come art history looks the way it does? Why did it take so long for humans to figure out how to accurately draw what's right in front of them? That's because it's HARD, because what we see is strongly colored by our preconceptions (see art history: when babies were painted as tiny adults, because there was no concept of "childhood") and because the world around us is influenced by so many laws of nature that we first need to discover them in order to portray them (see three-point-perspective). And that has taken tens of thousands of years. Just imagine that!
Even fantasy creatures are made based on references. It's just a bit more concealed. A classic western dragon, being an obvious example, might take scales from lizards, wings from bats etc.
What you're doing when you're not using references is going off your memory, which is based on extremely casual observations of the world around you. Because honestly - when did you last measure out the proportions of chairs to the tables they stood next to? Or the height-width-depth ratio of your classroom? Or the way the light bounces off the paper you're writing on and reflects on your hand? Probably never. So what's the harm in strengthening that memory? Good artists who can draw without reference can do so because they have a strong visual library that they have built through life drawing and reference drawing. For example, they know exactly how the planes of the face work, so they don't need to guess and can just jot down a face in a jiffy!
Now don't take this as an attack - I'm just very passionate about this theme! I just want to share the wonders of references with all the struggling artists out there! x)