The big question is how should the government allocate the funding for basic research between career stages to maximize the benefit to the society.
If you focus on training PhDs, which is the American way, you get a steady stream of new people with fresh ideas. But then most PhDs must leave the academia after graduating.
If you focus on postdocs, you get more value from the PhDs you have trained. Most will still have to leave the academia, but it happens in a later career stage.
If you focus on long-term jobs, you have more experienced researchers working on longer-term projects. But then you are stuck with the people you chose before you had a good idea of their ability to contribute.
If you focus on training PhDs, which is the American way, you get a steady stream of new people with fresh ideas. But then most PhDs must leave the academia after graduating.
If you focus on postdocs, you get more value from the PhDs you have trained. Most will still have to leave the academia, but it happens in a later career stage.
If you focus on long-term jobs, you have more experienced researchers working on longer-term projects. But then you are stuck with the people you chose before you had a good idea of their ability to contribute.