What motivates spending?
I think that we spend for the experience of choice. In other words we spend our money on whatever will make us feel wealthy and the way to do this is to choose the premium option.
A poor person is more likely to buy Heinz baked beans than a rich person. This is because the poor person can gain an emotional payback from making this small premium choice. A rich person would only get this sensation from shopping at Fortnum and Mason.
I do not blame the poor for their poor choices. They are only acting out a universal human need. The poor know that lottery tickets are a bad investment- but who can live without hope? They know that sugary foods are poor value- but who can make it through the week without something to look forward to?
The rich may sneer because they shop at ALDI and have savings plans in place of lottery tickets. They know that they are better shoppers are better money managers. It is easy for the rich to be rational in small things because they have full lives and not eating a doughnut would not leave much of a gap in it.