That's a good way to use debt, but far from the only rational one. The best reason to use debt is for consumption smoothing. For example -- a car breaks down unexpectedly, and now the owner can't make it to work. They won't get paid if they don't go. "Save up for a repair" doesn't work. This is perfectly legitimate reason to spend now, pay later. It's the canonical reason to use credit. The asset they buy -- a new alternator, or whatever -- isn't going to appreciate. The interest they pay is simply to pay for the service of having money now instead of later. That doesn't mean it's foolish.