I'd suggest that these groups are less distinguishable, or that there is more overlap of these groups, than you may think.
One the one hand it is infuriating to see them pay more for everything they buy because they are paying interest on everything they buy partly because they buy stuff they don't need or buy it sooner than they need to.
On the other hand there are incredible cultural pressures in america to spend spend spend and get newer/better stuff than you need (cars, houses, phones) and almost no cultural pressure to be prudent and responsible.
Probably doesn't help that there is a whole 'industry' whose only function is to capture 5-35% of the income of the poor and distribute it to the rich.
It often does make sense for many people to take out a loan to buy a car, but car loans tend to be described to people in terms of 'monthly payment' rather than total cost, which makes it easier for people to make bad decisions (e.g., buying that new $30,000 SUV w a 5 year loan instead of the used $15,000 sedan w a 2 year loan).