How is it possible that 50 years ago a HS Diploma was enough to get a good job – but nowadays degrees arent?

By the 70s a HS diploma was often enough to get a good paying job – nowadays a degree isnt. What happened? If an HS Diploma was enough and then people do the extra step to get an HS diploma + a degree – why cant they get the same as people 50 years ago with just a HS Diploma – its just unfair.