Man, over the last couple hundred of thousand of years, has been conditioned by evolution to require certain outside parameters to experience a happy life: access to fresh air, beautiful nature (why do you think simply looking at it lifts the spirit), close and nourishing relationships with other people, a fair measure of physical exercise, etc.
The modern world, however, forces people into the most un-natural surroundings and forces them to live in ways not in tune with their ancient history: living, cut off from their peers and their natural habitat, in tiny boxes in concrete jungles, sitting still for eight hours a day doing work largely inconsistent with the much more physical "work" of their ancestors. The family structures that lent them stability have largely been disbanded over a false notion of freedom and women's lib, spread out over vast geographical areas or simply abandoned in pursuit of the false gods of money and success.
It is no surprise this makes people unhappy. The sad thing is most people are unable to realize even why they are unhappy and make the right changes to their life style.
The marketing machine jumps in on cue and exploits the unhappiness: hey are you unhappy? Buy this monstrous car, it will make you feel safer. It will make you feel better. Eat these psychopharmaceuticals. Or just eat, eat eat our salty sugary comfort food. Watch these bullshit shows. Buy buy buy buy buy. And all the while the true root of the problem lies unadressed, providing fertile soil for the bullshit marketing system for ever.
Will people ever wake up and start living again in a way consistent with their history, and experience true happiness?