We finally have an answer: The beginning and the end of the sliding motion that produces static electricity experience different forces – resulting in a charge differential between the front and the back that results in the crackle of static electricity.
I had wildly different experiences with teachers within my own schools growing up. There was legitimately no standard that valued this kind of nuanced exploration of the world. Just a focus on standardized tests. It was almost entirely on the individual teachers to spend more of their time and effort to go any further than that.
I had some great teachers that made everything interesting and taught us more like the classes I eventually had in college, but I definitely have had more that were like this one math teacher I remember who, when I asked about why we had to do a math problem in a specific way we were learning about, answer something along the lines of “because I say so.”