Classical enumerations mention usury, wrongful consumption of an orphan's property, theft, intoxicants, and fornication. These offenses protect different interests: property, sound judgment, chastity, and family relations. They therefore cannot be reduced to one rationale or assumed to carry an identical penalty.
For example, theft and misappropriation of an orphan's property are both financial wrongs, but their legal elements and proof are not identical. Identifying a major sin is a theological or moral classification; deciding whether a particular legal penalty applies requires separate juristic conditions.