Here's another reason if you need one:
The type of fabric you choose for your garment is not only important for the feel and look, it can make a big difference to the way it screenprints too. AS Colour specialises in fine combed cotton fabrics, which are designed specifically to screenprint better than basic carded or uncombed cotton. Combed cotton has more of the fibre removed in the knitting process, which means printing inks sit much more cleanly on the face of the shirt after printing. A better fabric can mean the difference between an average screenprint and a great one.