Approximately spherical transparent objects are common. Approximately cylindrical and spherical reflective surfaces are common. Situations where you can apply high school physics are very, very common. Most of us just don't, because we're not trained to do so. We're trained to do the homework problems and answer the test questions. But don't we learn this stuff so we can use the knowledge in life?

I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard

So you're over halfway there. Now we collectively have a chance to learn the meta-lesson about applying knowledge.