I can see that. It's a good enough reason for me. In my head, I imagined it like boiling impurities out of liquid. Get the glass hot and melty, the impurities

I can see that. It's a good enough reason for me. In my head, I imagined it like boiling impurities out of liquid. Get the glass hot and melty, the impurities and glass separate due to different melting points, blah blah, blah. But if that doesn't happen and it doesn't affect the integrity of the glass too much, I can see the "Screw it" attitude of just letting it be.