I haven't seen it happen well, but I'd like to think retention policies, especially somewhat tight ones, could encourage folks to move durable information elsewhere. If you know this explanation is going to be removed in a month or a few months, you know to polish it up somewhere else.

Most stuff in slack should be ephemeral enough to not need that process, but I know that in reality that process never actually happens because the one that needs to move it doesn't have any incentive to do so, and it being deleted doesn't really harm them either.