The only medium designed for divided attention

Audio is consumed while something else is happening, and that changes everything about how it should be built.

Reading requires eyes. Watching requires eyes and usually stillness. Listening requires neither, which is why it is the one form of learning that fits inside the parts of a day that were otherwise unavailable: the commute, the walk, the washing up, the long stretch of manual work. This is the medium's real territory, and it is enormous. It is also the reason that audio built as though the listener were sitting quietly with nothing else to do is audio built for a listener who does not exist in the numbers that matter.

Divided attention is not weak attention. Someone walking may be following closely. But their attention is interruptible in ways a reader's is not: a road to cross, a pot that needs stirring, a person who speaks to them. The interruption takes a few seconds and the sound does not pause. What was said in those seconds is gone, and unlike a page there is nothing to glance back at. Every piece of spoken explanation is therefore delivered to somebody who will miss parts of it without ever choosing to.

Building for that reality means accepting a lower information density than a written equivalent would carry, and treating that as correct rather than as a failure of ambition. The same idea can be stated, illustrated and restated in different words without the redundancy feeling laboured, because the listener is not comparing your sentences to each other the way a reader does. Written repetition looks like padding. Spoken repetition is the only mechanism the medium has for surviving the conditions in which it is actually used.