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Theoretically, credit should be used for one thing: to make more money.I disagree.
You use credit to buy a car or buy a house when you don't have the cash to buy them up-front.
It's not so you can use them to make money, it's so you can use them to enjoy life.
> At some point, you run out of hours available and the house of cards collapses.
Only if you go too far. The point is to buy things knowing what they'll cost monthly and for how long, and to budget those as part of your monthly expenses. As long as you can always handle those, you will never run out of hours available and it's not a house of cards. Nothing collapses. You pay off your car; you pay off your mortgage.
You seem to be treating this as something black-and-white when it's not. It's an incredibly useful tool when used with budgeting. Not "to make more money" but to have a better life for you and your family for when it matters the most. Nobody wants to wait until the kids have graduated from college to be able to buy their first house.
And even with credit cards -- yes you generally want to be paying them off in full monthly. But if you want to take a vacation a couple months before you could otherwise fully pay for it, it's really nice to have that convenience too. Not to mention covering some expenses for a few months if you lose your job. They're a tool to be used responsibly.