The important thing about a lot of psychiatric ailments is that people have effectively lost some mental resource that they require to "bootstrap their way" out of the problem. Like, depressed people are usually too depressed to manage to make it to their therapy appointments (which they agree help with their depression, but only if they go...) So just prescribing talk therapy won't do anything; the person can't manage to "take that medicine" correctly.

Psychiatric drugs are great in the same way crutches are great: they let you "take the weight off" the problem, so you can work on the other parts of it. SSRIs let depressed people make it to their CBT therapy appointments. ADHD medications let unmotivated people get a job doing something they're passionate about. Anxiolytics let people make friends to attend social gatherings with. Etc.