Growing up as a kid who ate a lot of junk food, I think there's just more commonly a culture among less affluent folks to prioritize rewards now instead of rewards later.

Eat, drink, be merry today - you may not have the opportunity tomorrow.

Treating yourself or your kids now is the good life for a lot of people - of course, at the expense of tomorrow, but that's not too much of a concern.

So, a difference in priorities and perspectives among rich vs poor. Like the articles states, but a different view of it.