I disagree that the authors return to wastefulness/consumption is a result of systemic forces. I think it’s more likely the case that when you have a higher rate of income you spend money to convenience yourself and save time/energy because you value your time/energy at that higher rate of income.
Agreed, but the way I put it is that the higher consumption is done to compensate for the stresses that come with the work life(style). I have a lot less patience and mental energy to do impulse control or to judiciously weigh the pros and cons of this versus that purchase when in a stressful work environment compared to when I'm not. I'd say that counts as "a result of systemic forces".