Because sketches also deserve some love
Sketch: A hasty or undetailed drawing or painting often made as a preliminary study.
We all love finished works of art, don't we?
It's always so great to feel mesmerized by the amazing work an artist inverted on a piece, taking care of every little detail, managing to combine colors, textures, shadows and lights, to give as a result a masterpiece you could stare at for hours, immersing yourself in those details.
But just like a living creature, every masterpiece started little and grew slowly, it matured to reach that state of greatness but started humble, and just like a living creature that at one point was a baby, every masterpiece started as a sketch, an unrefined doodle on a piece of paper or a digital canvas.
However who said a sketchwork couldn't be just as impressive as a finished piece?
While looking at the finished product is always a delight, sometimes looking at the "naked lines" without inks of a comic page, the initial study of a character or a "work in progress" can also be interesting and leave you in awe. It gives a different feeling from the finished piece because there are always details that can only be seen when the artwork is still on the sketch phase.
Nothing tells more about the passion an artist pours on a piece of art like those textures and imperfect lines only possible with an old school pencil. Unless you're a drawing machine, you never do a line just once, you always make a line, then erase it, then make it again, then erase again... but those lines you erased never really leave, they are still there, only vaguely visible. Those almost imperceptible details now form part of your work and are what makes a sketch so great.
That imperfection is the beauty of a sketch.
Not all sketches are unfinished pieces
Another definition of sketch includes: "A drawing or other composition that is not intended as a finished work, but a preliminary exploration" (Wikipedia)
As mentioned, every piece of art starts as a sketch. However once in a while a sketchwork is intended from the beginning to never become a finished piece... or more like the sketch is the finished piece.
Sometimes a sketch is a perfect work of art by itself just the way it is, so the artist doesn't dare to spoil the perfection by adding inks or paint, colors or vectors. The sketch is just amazing in it's own way and no further elements or details need to be added.
So while many people associate sketch with unfinished and thus not of the same value as a finished piece, let's remember next time that sketwork has its own beauty and value, and that sometimes sketches and doodles can be just as amazing and impressive as their finished counterparts.
Links of interest
Some deviants with amazing sketchworks
Some Sketch-focused Groups
Elite-Illustration (that has a subgallery dedicated to sketchwork)