I don't know, maybe DI frameworks don't always work on private variables?

Annotation Processing based like Dagger 1/2 usually need at least package-private visibility for direct access to a field without reflection

But really, with Kotlin one should just use constructor injection anyways 🙂

Kotlin doesn’t change the fact that you don’t always control the object creation

Usually it's either you yourself or the DI framework creating the instance, is it not?

On Android you have the concept of activites which the system creates

Not always, sometimes you need to work in a Framework environment which controls lifecycle of some components

Android is a different story, true 🙂