“[Lean] starts with the customer. Always ask, ‘What value are we adding from the customer’s perspective?’ Because the only thing that adds value in any type of process—be it a manufacturing, service, or development process—is the physical or information transformation of that product, service, or activity into something the customer wants.” 

The Toyota Way 2nd Edition by Jeffrey K. Liker (McGraw Hill, 2021) p. 14.