It's that same casual carelessness you see with people leaving their nice stuff out in the rain.

A buddy of mine watched a line guy at a tiny strip in Idaho refuel a Piper with the fuel cap just sitting on the wing... right before a gust of wind sent it skittering across the tarmac into a storm drain. They spent two hours with a magnet on a string trying to fish it out. Plane was grounded for a day waiting for a new one. Just a total avoidable mess.

Actually, I think checking for bubbles and cracks is a waste of time. You can't see the real stress inside the glass. The only safe bet is to just run a full kiln cycle every time, no shortcuts.