Which begs the question, why create an independent classification? The Abhidhamma is far from a neutral analysis, if such a thing is even possible.
As I argued cogently and persuasively, and not at all snarkily, in The Mystique of the Abhidhamma, much of how Abhidhamma is actually used in Buddhist culture is, in fact, magic and superstition. The rationalist terminology creates a think veneer over highly irrational beliefs and practices. And this is no modern innovation, it is fundamental to how the Abhidhamma has always been.
In this case, I think the Buddhists, especially the monastics, had to find a way of catering for the need to provide services for the dead. This means you must have a way to manage and control the taboo of the dead and those near death. By taboo I mean magic power.
The physical dead body is one of, perhaps, greatest source of taboo, and only an individual with comparable taboo, i.e. a monk, can hope to keep that energy within safe confines. Otherwise the death will escape and infect others, or cause all kinds of mischief.
By wrapping the death and post-mortem process up in a container of ritual and doctrine, the celebrant, who technically is a bhikkhu but is in fact acting as a witch-doctor, contains and channels the taboo. Hopefully they can shift it to a higher plane, where the taboo energy, which, like any natural force, is ethically neutral, can have a positive effect.
This process is quite effective, but has one slight flaw. There’s no such thing as taboo, it’s just a supersition. So to justify this tradition, we use the time honored method of explaining the whole thing in psychological terms. Instead of containing and channeling taboo, you contain and channel emotions. Which is fine, it works just as well.
The only thing is, we’re left with these odd echoes in ancient Abhidhamma texts, which are insisted on as “ultimate truth”, instead of accepted for what they are, records of different ways Buddhist have understood the Dhamma.