Traditional CLI programs are typical methods for procedural programming implementation, where the flow is determined by the programmer and code runs sequentially, one piece after another. However, UI-based OS applications determine the flow of programs based on user inputs and events, which is dynamic.

Long ago, when mostly procedural ways of programming were a hit, you would have to look for a way to move the control of flow from a traditional procedural way (the programmer dictates the flow) to external sources such as a framework or components that determined the control flow of the program. This is what is called IoC. It is a very generic principle and part of most frameworks.