I've thought a lot about this, and conclude that part of the reason for this is that it conflicts with our evolutionary psychology. Humans, like most primates, are strongly tribal. Within the family and the tribe we go by (want to go by) very different rules than with outsiders. Maintaining constant vigilance is both physically and psychologically draining. Under the strict behavioral customs and taboos, the tribe was essentially a 'safe' space where we could let our guard down. It was a kind of 'bad manners' to treat tribe members with distrust. The need to 'pressure down' is still as deep within us as it was with our ancestors.
The modern cybersecurity world goes against this instinct. Being constantly on guard wears us down, treating co-workers, who in earlier worlds would have been our tribal cohorts, as potential risk is not something our minds really want to do. Deep down we want spaces where there are no walls of suspicion, where we can be fully relaxed. As stresses get deeper the need for openness does as well ... soldiers in combat need to be able to sleep, knowing their heavily armed fellow soldiers are protecting their back. Trust becomes a matter of life or death.
I don't know what the answer is. The world we live in is getting psychologically far from the world of our ancestors (it's not the modern toys and technology that is changing us, but the basic rules of human contact.)
-- FORTRAN manual for Xerox Computers --