Passive voice can be a great way to get around overuse of "I"/"my" in first person.
How? "I was thrown against the wall by zombies" uses I, where the more direct, "Zombies threw me against the wall" does not.
There are loads of situations where passive voice is useful and some of the suggestions I've been given in the past for "upgrading" certain sentences to active were just plain daft.
CC Finlay has a good line about this--tools, not rules.
I agree. Sometimes you want to emphasize the process over the actor, or the actor is unknown (but the recipient of the action is known), or you want to
emphasize the recipient's lack of control or agency from their perspective. I'm not sure how it would be used to limit personal pronouns, though.
The reason why many writing instructors and experts rail against passive voice is because beginning writers often overuse it when a more direct sentence structure works better. In expository writing, journalism and so on, using it can seem like the writer is weaseling out of assigning responsibility or agency to those performing actions. Who hasn't heard a politician saying, "Mistakes were made," to avoid assigning blame to themselves? In fiction, it feels cumbersome and roundabout most of the time, but it does have its purpose, both in dialog and narrative.
Also, some disciplines are notorious for using passive voice in their academic papers. When one is writing their materials and methods section in a science paper, the desire to emphasize the process d de-emphasize the person performing it leads to insufferably dry, indirect prose. Journal editors no longer require, or even desire, passive voice, but many researchers still use it out of habit, or emulation of the style they are used to reading.