I suspect that some of this in the US was due to the strict liability imposed on civil aviation manufacturers in the US. It increased civil aviation safety, but demolished a lot of the civil aviation manufacturers.

In criminal and civil law, strict liability is a standard of liability under which a person is legally responsible for the consequences flowing from an activity even in the absence of fault or criminal intent on the part of the defendant.

It made manufacturers very risk-adverse, placed overwhelming weight on being a known, mature design.

GARA later rolled back some of this, but things never really returned to their original state.

https://en.wikipedia.org/wiki/General_Aviation_Revitalization_Act

The General Aviation Revitalization Act of 1994, also known by its initials GARA, is Public Law 103-298, an Act of Congress on Senate Bill S. 1458 (103rd Congress), amending the Federal Aviation Act of 1958.

General aviation aircraft production in the U.S. – following its 30-year peak in the late 1970s—dropped sharply over the next few years to a fraction of its original volume—from approximately 18,000 units in 1978 to 4,000 units in 1986. to 928 units in 1994. (In a 1993 speech, Sen. John McCain said “nearly 500 last year [1992]”.)

General aviation aircraft manufacturers in the 1980s and 1990s began to terminate or reduce production of their piston-powered propeller aircraft, or struggled with solvency.

At the time, industry analysts estimated that the U.S. decline in general aviation aircraft manufacturing eliminated somewhere between 28,000 and 100,000 jobs—as unit production dropped by 95% between the 1970s peak and the early 1990s—sharply different from other segments of the global aerospace industry, where U.S. market share was still strong.

Product liability costs

Those manufacturers reported rapidly rising product liability costs, driving aircraft prices beyond the market, and they said their production cuts were in response to that growing liability.

Average cost of manufacturer’s liability insurance for each airplane manufactured in the U.S. had risen from approximately $50 per plane in 1962 to $100,000 per plane in 1988, according to a report cited by the Bureau of Labor Statistics, a 2,000-fold increase in 24 years.

Rising claims against the industry triggered a rapid increase in manufacturers’ liability insurance premiums during the 1980s. Industry-wide, in just 7 years, the manufacturers’ liability premiums increased nearly nine-fold, from approximately $24 million in 1978 to $210 million in 1985.

Insurance underwriters, worldwide, began to refuse to sell product liability insurance to U.S. general aviation manufacturers. By 1987, the three largest GA manufacturers claimed their annual costs for product liability ranged from $70,000 to $100,000 per airplane built and shipped that year.