That’s all well and good, but the complexity comes with navigating life obligations (rent, school loans, etc.) and long-term compensation (equity). Just waking away because of the talent shifting or similar is a nice concept but impractical. This advice read more like a guide to working in your 20s.
I think that it’s easier to change jobs in the USA; we usually don’t have a contract for a notice period for leaving. But like anything important, changing jobs takes preparation and a lot of effort. One might say that they lack opportunity or have too many obligations, or one might say that they just haven’t finished preparing for the change.
If I quit I don't get unemployment benefits. Eventually there is some money, but I'll have to first spend my savings and eventually sell my house (it's not enough money to pay the mortgage). This in western Europe.
I think in the US you have the 'benefit' that jobs are not very protected. Hiring is thus more flexible. Downside of course is that firing is too.