Some of them experience so much too early and simply burn out.
Some of them don't open enough new doors.
Some of them have unchangeable biological states.
Some of them are frightened.
I agree with your considerations above Professor Spendius.
However, I note your experience regarding your cousin. Consider this ; -
The Want factor.
Keeping up with the Jones's
Television programmes and advertising.
If people find themselves lacking in being able to show off their acquisitions of being up to it, it creates total impotency. Depression is a symptom
formed by despair at personal failings. Ennui, is an escape route. Having no faith in ones self creates both boredom and depression. The sufferers may well decide to wile away the rest of their lives being fed and watered, and excused ALL duties. The old lag afraid of missing his Christmas dinner will throw a brick through the shop window next door to the police station on Christmas eve. He will get his dinner. There are those who enjoy spending Christmas day in hospital too, they could even get on television if Jim Davidson pops in to make them laugh.
Not really, it keeps a great number of people in regular employment, nothing terrible about that Professor!
Ennui - wouldn't this be an excellent name for some famous-persons newborn baby? Anybody pregnant? Let's suggest it.