Let me explain.....
Most new chains are now cheaper than the charge to sharpen them plus most chains that are brought in to us are blunt because they have hit something (stones, concrete, metal, wire etc.) which has not just made them blunt, but also damaged them.
Sharpening a chain with side damage will produce a sharp chain that will not cut correctly, and will bite to one side making it dangerous to use.
Sharpening a chain that has a small number of links with top damage (as a result of hitting something) will cause a chain that will stutter making the saw vibrate and dangerous to use.
From a pure health and safety point of view we would rather replace a worn or damaged chain rather than giving you a sharpened chain that could kill you.
Most of our "domestic" chains (up to 16 inches) are around £8.50 each but the charge for sharpening it is £10 - so also from a financial point of view it doesn't make sense either.