The lack of disposable income is greatly overstated. In the US, the median disposable income is ~$1000 per month. This is the money left over after all normal middle class expenses are accounted for i.e. money you can save or spend on luxuries. And the average disposable income is twice the median.

While it is true that there are many Americans with little or no disposable income, that does not apply to the majority of Americans.