Most people lump all kinds of negativity under "depression" without realising it's not an umbrella term for feeling a little bit unhappy sometimes. There are serious disorders of the brain that are chemical imbalances which can be rectified by chemicals. The brain is just a lump of tissue like any other bodily organ. If there's something wrong with your heart, you may need to take medicine for it - the idea is as simple as that but the practice is fraught with complications.
The definition of what depression is has changed, though, and the problems with medication is that it is very hit and miss. The "science" behind anti-depressants is still very much in infancy, although the commerce of it is very much advanced. It's hardly surprising that "well being" is now a commodity that you can buy, although not always with medication - lifestyle, holidays, consumer items, then of course the medication when none of that inevitably works.
It can take a while to find the medicine that works and others can exacerbate problems. I was on a medication that was almost instantly successful which, when I researched it, had a very low success rate among other users.
But medication on it's own only has a certain success. I was told by my doctor that the best chances of defeating things like depression and anxiety* is a combination of medication and counselling. Either one on it's own can be successful, but in tandem there's a higher chance.
(I do think it's interesting that there's a political partisanship sometimes - Bitewerks MTB writes of "a fairly extreme conservative radio host" who basically seems to be claiming that since you'll never be happy all the time, taking medication and spending a fortune on counsellors is often a mistake. Whereas a lot of "fairly extreme" left-wing friends of mine used to simply blame society for any time they felt unhappy, which of course meant all the time. I'm not convinced that political opinions are helpful when making psychological assessments - I'm also not convinced they're a million miles away from each other).
* Anxiety is very much an evolutionary instinct that none of us would be alive if not for. The problem with a lot of people, myself included, is that it can be over-worked compared to one's actual life activities. It is a very physical thing - if you've ever felt something like a rush of coldness or tightness in the chest area (and if you haven't, why are you alive?), that's adrenaline rushing through you, preparing you for fight or flight. A constant stream of that adrenaline, many times for no real obvious reason, is anxiety. Apparently it's called "flooding" sometimes.
Fear is humanity's greatest ally and enemy. There are very good, sound, evolutionary and modern-world reasons for it. Hatred is a common reaction to fear, which is pretty much why humans are the kind of species we are. I know many people rate lust much higher than both of those, and would place fear, hate and lust as the foundation stones of human behaviour, as it where. Personally I think lust is important as a driving force but not as strong as fear - the prerogative to survive is stronger than the prerogative to reproduce.