>Yet average stress level seems to be getting higher and higher.

An important point is the occurrence of "Dominance Hierarchies" which has been persistent in animals/human since the dawn of time. In a small hamlet, it was 'easy' to become known as the best blacksmith, the fastest runner, the best storyteller. You physiology literally changes and you gain an increase in dopamine receptors.

With the rise of technology, we are exposed to Dominance Hierarchies of much grander scope. Kids (and adults) are evaluating themselves against Instagram models and NFL Stars. A 14 year old can win their local brazilian jiu-jitsu tournament and still feel inadequate.