In 1950s, most people did not even go to college, let alone grad school. The people who went into science in 1950s were not in it to “get a job”.
These days, many students see grad school as the simple next step after undergrad, because the job opportunities are not good for many new grads (eg biology bachelors).
We therefore see a huge influx of phds and academics, but they are entering academia for different reasons (careerists) than when people did it in 1950s.