Well yeah, it's still debt. It's still the unpaid balance of the cost of goods and services.

The essential purpose of a market for IOUs is to allow us to issue a lot more IOUs. This is critical to the industrial and technological development that has allowed us to stop living in the dirt. But liquid debt markets can also be weapons of mass destruction by allowing misallocation to compound into ruinous financial crises. Sort of like, oh I don't know, bloated, inefficient government entitlement programs funded by massive debt that can only be dealt with by a.) confiscating the labor and assets of the population by force, or b.) monetizing the debt and inflating it away, which is itself a backdoor tax on the same population.