Hmm. This sort of goes well with the idea that propagation is hard. When a mathematics student is first studying a subject, they tend to start off with a very specific view of each new skill they pick up. Only with time and experience does one propagate the skill throughout other domains of knowledge and come to use it in the real world, saying "Hey, I bet if they altered the shape of the packaging here they would save money! I can do the optimization problem in my head, why didn't they think of that?"
Today I learned that you can toast marshmallows in the oven.
By "learned", I mean "I read a recipe which included as a step toasting marshmallows in the oven". I didn't have to try it out to realize that this would obviously work. It was plain as soon as I heard the idea. And it shouldn't have needed pointing out. I know how ovens work. I am familiar with the marshmallow species of food. I love roasted marshmallows while hating them in most other forms and often occurrently lament the difficulty of arranging open flames over which one may safely toast them. I routinely try new things in the kitchen to get results I want.
And yet I read it, and was surprised. And so were the people I reported this finding to. It needed pointing out.
What other facts need pointing out, although they are plain on inspection? What is the pattern behind these facts and a good way to find more?