Sometimes your mental state is so bad you can't make any decision or improve your current situation. Maybe you're working during the day and dealing with your family the rest of the time and feel stuck and sinking. Antidepressants can help dissipate the fog in your mind, allowing you to think clearly and actually make the decisions you needed to make and improve your live to a point where they are not needed anymore. You also talk with the doctor prescribing the drugs, if it's not improving how you feel they will suggest other solutions.
Also I totally agree with parent. Decent material conditions and the knowledge that they are stable are absolutely needed for a healthy and flourishing mind.
Anecdotally, I’ve gone off Zoloft after years of daily use without any side effects more seriously than temporarily being a little mopey.
As for benefit … we’ll, in raw numbers plenty of people see some benefit. Given the low side effect profile they’re worth trying as a first line of defense for therapy-resistant anxiety and depression. Particularly severe depression may require interventions such as ECT, but for mild to moderate cases a combination of an SSRI and CBT is often pretty effective.