Hi janshares! How's it going?
Keeping to the United States, we can start by noting that, like the "mother country," England, this country's early history from the foundation of the republic, is very much informed by the Protestant Reformation, the so-called "Protestant Work Ethic," and Calvinism, which is to say Protestant Calvinism.
The idea was that no one knew who was "saved" or not, only God knew who was going to hell or heaven upon death. But people can't stand not knowing something, not having an "inside track," as it were; and so, one of the social manifestation of all of this was the idea that solid material prosperity, if not wealth, gave some indication that one just might be one of the lucky few "saved."
Material prosperity gave an indication that you had avoided "Sloth." And you have to remember that Sloth or laziness, was regarded as rather a "gateway" sin, one which made you vulnerable to the others: "Idle hands are the Devil's workshop."
So, if you were material prosperous, if not rich, you had, apparently, not only avoided Sloth but, perhaps, many of the other sins which Sloth opened one up to. I suppose the idea was that if one were lazy, he would get into other activities which would unleash feelings in him of Envy, Gluttony, Lust, Pride, Anger, and Greed.
After all, Envy is wanting what someone else has because you are not satisfied with what you have (though I can't go along with the idea that inequality of wealth and income distribution in the United States is due to "sin'); Gluttony can involve using food to fill an emptiness in one's life (indicating that the person may need to work harder to create a full life, and all that); if you Lust after, say, the wife of your best friend, this may indicate that you need to work harder on your own marriage or relationship; and so on and so forth.