The fact that I am not a smear at the bottom of a tall building is a direct contradiction to your statement and shows that they do for some people. No, I was going to 'get better' without help. Yes, I fed trolls.
I was already there before the antidepressants kicked in. I would look at something and evaluate how much it would hurt, if it would work and what state I would be left in if it only kind of worked. I was also objectively in a good spot. I had a full time job with good people, a loving partner, a stable place to live, no kids and very few other stressors. I realized that there was very little I could do that I could summon the motivation for so I sought help. I was referred to a psychiatrist who put me on Prozac. There is a phrase that stuck with me that he said. He said it would give me a 'thicker skin'. I think this was key since every comment that was directed my way was over analyzed to look for signs of insult. It was as if everything in the world had a negative pressure on it. I think of it as events that happen like objects floating in water. The surface of the water is the neutral point, neither good nor bad. A comment would be like a ping pong ball, almost completely positive. Through my distorted view, it would be like a 10g weight was attached to it. It would become 90% negative and I would wonder what had prompted it. The antidepressants removed a lot of that weight so I can evaluate things without that bias. I feel like this is what people mean when they say they're drowning in sorrow. There is a weight attached to everything that makes the events more negative, less uplifting. The things that normally are buoyant don't support them anymore. I think it's the same for depression except that in sorrow, the cause is usually obvious. In depression, the swimmer is on their last few kicks. At worst, they've turned to temporary relief in the form of hard drugs that makes them bob.
I've said before that I think a lot of people that think they suffer from depression are actually suffering from despair. I guess the more clinical term would be situational depression.
It's understandable to constantly feel anxiety over rising rents and living expenses in the face of flat wages, and their constant poor mood from the stress makes them think they're suffering from depression, and they'll seek help. But a Prozac or whatever won't make you feel any better about having a 2-digit bank account after paying the bills.
The underlying cause is that my brain is broken and we have a century worth of genetic evidence that it is simply a heritable thing to have a brain broken in certain ways.
I get "sad" if the day is short FFS. Sure that's understandable from a biological perspective, but pretty incompatible with living at a high latitude with long winters. It's a genetic defect.
I think antidepressants are only part of the equation but many stay on them and don't fix the underlying causes.