I have a question about favor, and how it is distinct from debt.

I have a question about favor, and how it is distinct from debt.

I have a question about favor, and how it is distinct from debt. The system of debt make sense to me, but I fail to see how favor is not just negative debt .

Characters with a sworn allegiance, they have 3 debt and 1 favor with a faction. This would imply that there is a distinction, but how is that different from just having 2 debt?

Is calling in a favor by using a point of favor instead of incurring debt different? Otherwise, what does having a favor do that not having one less debt would allow?