There is only one valid definition of a business purpose: to create a customer.
Personally, I dislike the term “user” because it does not respect those who engage with products, rather it makes those who use computer products sound like drug addicts. That said, “user” is the term the IT industry has adopted. No other term is as widely known.
The term customer is a potential alternative to user and does command respect. However, I think the two terms are used to describe different types of people.
Both customers and users—whether the terms describe the same people ...