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?”
Songs are made from repeating patterns of beats and melody. The time signature tells you what that pattern looks like. If you just memorise all the notes I suppose it matters less. But if you wanted to improvise like with a guitar solo or whatever that’s the rhythm you can use to improvise with.
It’s the rhythm equivalent of the key/chord progression for the melody. If you know the chord and when/how it changes through a song, and you know the basic rhythm building block you can just make up notes that are guaranteed to sound great with the other instruments playing.