You'd buy your meals in diners instead of buying food to cook, if you were someone non-wealthy working in a factory or an office. You probably wouldn't be buying that much outside of this: for cigarettes, newspapers etc. there were newstands you could shop at while running to work. For big purchases, I imagine you would get a day off. Buying a fridge would be a major event, for example. But also one I'd expect people to be married for already.

Besides, if we go back far enough, upperish middle class people would hire servants. The original 101 Dalmatians film comes to mind.