The solar cells are tightly glued to the glass. Glass is easily recyclable but obtaining it and cleaning it is nearly impossible. It's also treated with antimony to increase its durability which limits how you can handle it. About 90% of all glass in solar panels has been landfilled.

A minor point anyways. Glass is not exactly a precious resource.

The most valuable parts are obviously the silver (about 50% of a panel's scrap value despite being 0.1% by weight), aluminum (about 20% of value), silicon (about 15%), and copper wiring (about 10%).

We are only just beginning to figure out techniques to reclaim the silver using thermal heating and chemical leaching techniques