It has little to do with interest, only context. It has nothing to do with perceived distance from the action. Euphemism is more clearly a distancing strategy, for example, than passive. In addition, passive voice causes wordiness, and it draws attention away from more important words in the sentence. Wordiness is a relative term.
Passives are typically two words longer than actives if fully expressed.
If the agent has been deleted, they are less wordy. Passive is simply a device for changing emphasis. You cannot interpret it or explain it unless you are at least in the context of a paragraph. In single sentence contexts, all explanations fail.