When the plant has been harvested, you have effectively killed it. The light is important for providing the energy for the plant to fuction properly and grow. When you're drying and curing, you don't really want a bunch of light as what activtaes the chlorophyll in the leaves etc. Ideally you want all that stuff gone, as it taints the bud and makes it smell/taste grassy.
There are some threads around that give more educated answers to issues surrounding light, and ideal harvesting-curing conditions. You should take a look at them.