[0] consumption = autonomous consumption + marginal propensity to consume × disposable income

Even when income, disposable or total, is set to zero, individuals still have to eat, to be sheltered, to take transportation.

Then, wherever there are multiple products for anything that would be considered a necessity, advertising can still have a positive return.

[0] https://saylordotorg.github.io/text_macroeconomics-theory-th...