It wasn’t always like that in the US. Three year doctorates are still a thing in the UK and in Germany. Lower the standards for a doctorate and make a postdoc a formal necessity for a job as a professor, rather than not formally being one but practically so. You can even call it a habilitation, like the Germans do. If you want a doctorate go for it. If you want to teach at university after you get your doctorate you need to basically do another one, but it’s called a habilitation.