It was pretty specific that the pages were themselves gold sheets with the writings being tiny engravings. If that were true the most logic reason would be high tactility. As the most tactile substance known it can be hammered to within 6 atoms thick before tearing, though it also means gold warps and bends with low effort. When hammered thin enough it can resemble a fabric and with modern equipment can be thinned into a fully transparent electrostatic film.