It’s both. However, money was backed by gold, then the Fed was created and diluted purchasing power. Additionally, wages haven’t kept up with inflation over time and pensions have largely gone away. Before, people didn’t have to plan for their own retirement. Today, they do. Formerly, they could choose a big company and choose to work there 30 years. Today, you get fired if you start making too much money or get above 50…they want to trade you in for two 25’s that still (combined) make less than you. Lots of headwinds facing people after the 1970’s/80’s that didn’t happen formerly.
HOWEVER, people are much worse at saving today than they were back in the day too.
Friedman is the only one worth reading.