> To finance their lifestyles, higher-income households are more likely to put expenses on credit cards -- but also more likely to be able to pay off their balance in full.
This means using cards as a convenience or optimizing for cashback (miles, status, ...) and not "to finance their lifestyles".
On the subject -- I am constantly surprised by the "you must buy as much house as you can afford, and then some" mentality in the US (I did not grow up here). I know several families, with 2 good professional incomes who loaded up on expensive housing to an extent that if either of them gets a noticeable pay cut they will be screwed. While there is still cheaper, smaller houses in the same town with the same school that they can handle on a single income (and invest or travel on the second; or just take it easy). So I am not particularly surprised that a high income family can dig themselves a financial hole. My 2c.