They wrap holes in the same material they use to contain the universal solvent.

The holes are there because without them it would make CDs look like donuts that have no holes: ridiculous. What's a donut with no hole for the love of Pete? It's just a stuffed pastry; a bun filled with jam or pudding, and IMO, that ain't a donut. Besides, when's the last time you even SAW a CD filled with jam? Oh, yeah, Pearl Jam, but like--anyway, I have lost my train.