Good point, but I think that doesn't explain the "why" of the graphs, this observation only explains the fact.
The "why", then, in my (also non-expert) opinion, is (once again) globalization: We produce cheap electronics in China, so phones get cheaper, while we maintain the same, relatively high expenses for products and services that cannot be outsourced to countries with cheaper work-forces.
And because those local products and services are already "overpriced" (relatively speaking), there is also no way salaries will go up and will just stagnate from an inflation-adjusted point of view.
First, income in the US for most jobs has stagnated, inflation adjusted. Second, goods and services that can be produced cheaply due to technical advances get cheaper. This did not affect education, and medicine probably only got more expensive. At the same time, globalization accelerated this process greatly, pushing the "globalizable" products' prices even more, which means the "localized" products must get more expensive. This is known since at least 1996 as the "globalization trap."
The "why", then, in my (also non-expert) opinion, is (once again) globalization: We produce cheap electronics in China, so phones get cheaper, while we maintain the same, relatively high expenses for products and services that cannot be outsourced to countries with cheaper work-forces.
And because those local products and services are already "overpriced" (relatively speaking), there is also no way salaries will go up and will just stagnate from an inflation-adjusted point of view.