For one, I also have family members who are very alcoholic and 'you'd never know it' either, i.e. fairly highly functional.

The effects of caffeine and nicotine are mild, and mostly physical. Especially with nicotine, it's a 'maintenance addiction' in that smoking in addicts is mostly to get to 'stay normal' because the body has adjusted dopamine receptors. A little bit similar with caffeine in that we build a tolerance.

I don't think it's a stretch to consider that there might be some issues with a good chunk of society walking around stoned all day. I'd put 'drunk' in a similar category.

The people who I know who are like this are themselves concerned but they can't seem to change their habits. It's not just a matter of 'physical/mental' state - they are basically different people in this mode and they know it.

> The effects of caffeine and nicotine are mild, and mostly physical

The primary effect of caffeine is mental alertness.

Mildly high isn't equivalent to stoned, and I don't think it's a stretch to consider that the might be some issues with everyone self-medicating for motivation and concentration with caffeine all day.

They seem to be alluding to some unknown effects of being 'kind of high', but I agree with you.