You seem to be assuming that modelling payments as sub-types is appropriate. It may not be, or not stay that way over time. Often one needs a buffet of independent or semi-independent features to be flexible. Hierarchy-centric ontologies, such as "types", are limiting.
Yes, I know types don't "have to" be hierarchical, but they are usually messy to manage as non-hierarchies.
Yes, I know types don't "have to" be hierarchical, but they are usually messy to manage as non-hierarchies.