It's as serious as a heart attack. Everyday billions of dollars, which represent immense man power and dedication, are spent in pursuit of the unearned. That means the goods and services you buy today are more expensive because every dollar you spend is competing with all that borrowed money. That alone is plenty bad.
I won't even begin to talk about the repercussions of bankruptcy (or runaway inflation) that you shrug off. Modern day Greece, pre-WWII Germany, Zimbabawe aren't/weren't tourist destinations for a reason.