For me it’s time signatures in music. I grew up playing instruments, played in several orchestras, etc. But no matter how many times someone tries to explain time signatures to me, it makes no sense. I don’t understand why people place such importance on it. To me, notes have a pitch and a duration, maybe some dynamics. That’s it. I don’t understand why people try to needlessly complicate it. It doesn’t give you anything.
My wife will hear a song and go “Oh neat, it’s in 5/8.” And I’m like “How tf do you know that, and why does it matter?”
Is this like, “I didn’t know you were mad” or “I didn’t realize I was supposed to tip my hairdresser” or “I didn’t realize they’d turn off our electricity if zi didn’t pay the bill”? The first is pretty complicated, but the second two are various flavors of “proactive research is part of maturity”.