The term maturity is frequently confused with the term "capability" (skill, competence). Capability refers to the degree of perfection with which a party delivers a certain performance, according to the definition of that performance. However, that says nothing about the value of that performance for the customer.
Services have only one goal: to create value. For that reason, USM considers maturity from the perspective of value creation. If we want to put value creation at the center of a maturity model, it is necessary to first define the concept of value.
Value is the change in the vitality of a system.
If there is to be added value, then the vitality of the system in question will have to be improved. Because this concerns services, the system here is the business operations of the customer ('the business'). USM follows the principle "Value is determined by the observer". The perspective of that observer, the customer, therefore determines whether there is added value.
USM's Value Maturity Model is described in detail in the USM Wiki.