The informality started fairly abruptly in 1964 or so, with Vatican 2, the SDS (Comintern phalanx) taking over the youth in universities, and just generally on the street and the media.
You could call it an op. If it was an op, it was perhaps the single most effective one.
Wearing a jacket and tie in an office or school is a very powerful signal to all the important people: employees, clients, visitors, investors.
It says that you all take your assignments and the mission seriously.
All of the above is borne out by experience and even research.
Bring back some degree of formality and uniformity in schools and offices and things start improving immediately.
If you are willing, look up old YouTube historical footage of Harlem street scenes in the 1950s.
What I say is true.
Another proof is if you wear a blazer and tie into a typical postmodern workplace you will find many people (almost always liberals) who immediately get hostile at your attire, they in their jeans, executive T-shirts, and precise three-day stubbles.
Clownish attire --It's an op. An effective one.
Its odd that people who are beneficiaries of a dynamic and advanced economy dress like some of the people who live in the poorest regions on earth (i.e., unkempt appearance, shabby pants, t-shirts, flip-flops).