For serious lectures (not story telling like history or other humanities) you can't be doing anything on the side if you want to understand. Try listening to a math lecture, or chemistry lecture while doing dishes :)
I found the same to be true with audiobooks, nothing serious can't be "just listened to". I've tried to "listen" to a good biology non-fiction on how live evolved from the primordial soup. Shit, in the first chapters there were covalency chemistry and other stuff that I needed to sit down and write to understand.
> not story telling like history or other humanities
Those are not serious humanities lectures. The serious ones are not storytelling, but serious examination of the evidence or of its analysis. There are far more factors, complexity, and uncertainty in an historical event or process than in a petri dish, and the event can't even be reproduced. It's impossible to use the same kind of scientific method and obtain the same kind of certainty, and requires far more critical thinking, judgment, and analysis.
What caused Andrew Jackson to be elected? There's a relatively simple story told, but the reality is enormously complex and uncertain.
Referring to "math" as serious just makes me want to discount your opinion entirely. Lectures (or indeed any linear encoding) are a bad medium for discussing formal languages. This has nothing to do with how much you care about a topic or whatever "serious" is supposed to imply here.
Regardless, listening to something intently and doing mechanical actions are not exclusive.
Well try to listen to a group theory lecture (for example on cohomology of groups) while doing chores :) But the lecture was indeed useful if you stop and rewind and see how the lecturer was explaining (there were some interesting graphs).
Your brain can't hold the context long enough to go to the required level of abstraction, while you're multitasking (may be walking or something deeply automated doesn't count.
I would say the main reason it's hard to follow abstract maths lectures by listening is not the difficulty of the concepts per se, but simply because it's so visual: it relies on notation and diagrams
But mathematicians can talk to each other about arbitrarily abstract concepts, as long as they have enough shared background, and they don't (always) need a blackboard to do it.
Conversely, you can have conceptually very simple things that are basically impossible to follow just by listening, like multiplying two nine-digit numbers or following one of Euclid's proofs in plane geometry. The difficulty isn't about abstraction, but how many things you have to hold in working memory
I found the same to be true with audiobooks, nothing serious can't be "just listened to". I've tried to "listen" to a good biology non-fiction on how live evolved from the primordial soup. Shit, in the first chapters there were covalency chemistry and other stuff that I needed to sit down and write to understand.
Too stupid to do it while doing chores I guess...