I look at it from a scientific perspective.
The 'goal' of most creatures is simply to survive to reproduce. Nothing more, nothing less. Humans are no different than any other animal.
The difference between us and other animals, is that we have developed a higher cognitive level with high amounts of self-awareness. Thousands of years ago, humans didn't have such a high life expectancy. It was an absolute necessity to survive and reproduce as soon and as much as possible. We had lower survival rates, and a lot more dangers to fear. But now, we have gotten to the point were we have not only prospered, but conquered the very earth itself.
So what is left? There's so many of us, and life rates are still at their highest no matter what health complications or accidents that are thrown our way. Illusions of self worth? The thought of what the average person does contributes to anything? However you may see it, there are BILLIONS of people living today. MILLIONS of babies born each day. As life expectancy rises higher and higher...the meaning of living lessens and lessens....
People fill their lives with what they THINK they need (money, love, careers), because ultimately most people actually CAN'T 'live' without it. We all have our own reasons to be depressed/suicidal. But the most common reasons I see (outside of finding life pointless or traumas) is the lack of love/relationships or lack of jobs/money. Really makes you wonder how things could be different if the flaws of today's society were fixed...
EDIT: Perhaps I was overestimating when I said millions of births... but if you go to
https://www.worldometers.info/ , the amount of births versus deaths estimated this year
alone is crazy!