All skill degrade with disuse. For example, here in Canada we have observed a literacy and numeracy skills curve that peaks with post-secondary education and declines with retirement.[0]
That is one factor, but it’s not the whole thing. The other key element is “cognitive offloading” where your brain stops doing stuff when it thinks it is redundant.
This is similar to the photo-taking impairment effect where people will remember an event more poorly if they took photos at the event. Their brain basically subconsciously decides it doesn’t need to remember the event because the camera will remember the event instead.
If the tool is reliable, it's a win. Saved brain power doesn't disappear, it can be applied elsewhere.
If the tool is powerful enough to do a better job than our brains would, it's a big win. In fact, we built the entire technological civilization on one such fundamental tool: writing.
Or from another perspective: our brains excel at adapting to the environment we find ourselves in. The tools we build, the technology we create, are parts our environment.
This argument has held up in the past but there’s no certainty that during this current period where LLM’s are not perfect (and in many cases far from perfect) - they can ever become perfect that it’s fine for one’s existing human capital to depreciate.
This is similar to the photo-taking impairment effect where people will remember an event more poorly if they took photos at the event. Their brain basically subconsciously decides it doesn’t need to remember the event because the camera will remember the event instead.