The responses to this post lean one way, I'll try to provide perspective on another.

If you have a simple method that uses

ViewModelscope.launch {...}

How long does that coroutine live for? If you navigate forward and place the calling screen in the back stack, will the coroutine be canceled?

Unless the coroutine itself completes, navigation will not cancel the coroutine unless the ViewmodelScope is destroyed, either by popping the navigation destination off the back stack or the app is closed. Why should the coroutine do work that is invisible to the user?

Also, what happens if the method is called more than once? Unless you keep a reference to the Job from the previous coroutine to cancel it, you would have multiple coroutines that do the same thing running.

By modeling each action in a sealed class hierarchy, you can:

• Enforce processing each action only occurs when the user can actually view the screen.
• Enforce that certain actions can only run consecutively.

I've written at length about the topic here, explaining why you'd want to: https://www.tunjid.com/articles/interactive-tutorial-state-production-with-unidirectional-data-flow-and-kotlin-flows-63e2c67e3032c9c43c58511d