Every art teacher will tell you, nothing matters more than an accurate initial drawing. The coloring, shading and the painting is never as important as that. Which is why the first course in any art school is DRAWING 101. Not painting. Not color theory. It's really quite difficult to mess up a project which has an accurate initial drawing. On the other hand, it is very difficult to make something look good which is not drawn accurately.
Drawing and shading require two different skill sets. When you're doing the initial drawing of any composition, you need to be looking at the entire picture. And the relative proportions and positions of each element. It requires attention, concentration, and keen observation of the reference picture. Shading, on the other hand can be broken down into different parts, and you can forget about the rest of the drawing. You can even forget your subject (in fact it is advisable to do so) and just treat the parts as abstract shapes and work on them individually.
When I first started, the initial drawing would take me so long, and I would get so many pencil and eraser marks on the paper and damage the paper, that I would give up before even starting to fill the drawing with colour or shading. Basically I hated drawing, and I loved shading. Shading was fun, and I was good at it. I sucked at drawing. So, I would take a print of the reference photo, put it on the glass coffee table and put my drawing sheet on top of that. Below the glass, I would carefully place a bright torch light, switch off all other lights in the room, and trace away! Quite an elaborate setup, right? I would trace as much as I could. All the outlines, sometimes even the shadows. And then take the sheet out and happily spend hours perfecting the shading. Of course, the end result was beautiful. Some of the best portraits I've ever made.
But that's cheating right? That's what you'd say. Slowly, I started tracing lesser and lesser of each drawing. I would only trace the outline of the face and the eyes. Then I would only put little dots where the eyes should be, and freehand the rest. And then I reached a stage where I didn't have to trace anymore! Yay! Level unlocked. Target achieved, right? Why then do I still trace sometimes?
Because I still dislike the task of drawing, and still love shading and colouring. But learning to draw has made me a better artist. It has improved my observation, it has even improved my shading. Which is why I feel that as long as you know you can freehand, it is okay to trace. And I'm waiting for that day when 100% of the time, free handing any drawing would seem much easier, faster and simpler to me than having to trace it off of my computer screen. But till that time, I'll free hand some, and trace some, and I'm just as much of an artist when I do either.