There is a given when it comes to telescope lenses for use on earth or in space. The bigger the better! A bigger diameter implies greater optical resolution and light-gathering power.
But making bigger and bigger mirrors and windows comes with some considerations for those wishing to deploy them, and for the companies charged with their fabrication.
First, bigger mirror and window size means significantly inflated cost, and this cost increase does not scale linearly. As the mirror size increases, costs increase exponentially. Second, in many instances applications demand that despite an increase in optic size, they need to be lightweight, and this may require that large scale optics be fabricated and mounted on an ultra-lightweight honeycomb structure, and this further increases cost.