Likely for the same reason why prescriptions are so popular. It is way easier to down a pill then to workout, changing your eating habits, or adjusting your lifestyle to allow for more sleep. Changing habits is hard, eating meds relatively easy... "So off we go, and man, if someone interferes with our narrative, we attack like the speedfreaks we have become..."

For some people better diet, exercise, and sleep require taking drugs to make it more likely they can even do those things. It's a dumb take.

and those are the very exceptions the parent allows for.

It's "fuck off advice". They recommend it in full knowledge that almost nobody ever sticks to it, but it keeps the advice receiver busy and feeling responsible for their own problem.

Lifestyle change is hard and impractical even for most neurotypical people. With untreated ADHD, it's almost impossible.