If you use a credit card, but can’t pay it immediately then you pay interest. It’s a trap the less wealthy fall into.

Spending money on don’t have with no financial repercussions is known as the elusive “infinity money hack”. Which clearly does not exist.

Of course there’s going to be a a cost to spending beyond your means.

Or you could simply not pay on the credit card, and avoid the trap?

The point is they make a lot of their money from people who don't, paying 20% APR -- the 'whales' in this consumer industry aren't the richest people, unlike retail, gaming, travel, etc.

Not everyone always has the money not to.

This isn't correct, rewards and benefits are not 100% funded by interchange fees. They wouldn't be possible without many customers paying interest.

What funds it is besides the point, you didn't understand.

Understand what? I'm responding to your claim as written in the context of the comment you replied to. Your current reply is just as vague and light on details so not sure what you were expecting.

The relationship is that the service and rewards you get are subsidised by generally poorer people who mess up their financial planning.

Rewards are paid out for transactions, not interest paid, that's all. Otherwise poor people failing payments would get more rewards than the rich which don't. The dynamics would be completely different.