My guess: the concept of "a length of an array" is the thing you use to think with when you need it. Why? Because it is a single entity(through abstraction).

My guess: the concept of "a length of an array" is the thing you use to think with when you need it. Why? Because it is a single entity(through abstraction). And because it is a single entity and you use it a lot, it gets connected to many other concepts. And because you've solved problems with it,it has more emotional value. This means you can more easily retrieve it and it has more "meaning"/context to you. list.length gets used less often and it just a concrete implementation of the concept so maybe it's just linked to the concept. And it's also more complex to remember and use because it's made of 10 items.