Subreddits are built upon user activity, and need active moderation to keep that under control. A policy of allowing the subreddit to be passed on to a new moderator if the previous moderator is gone -- which doesn't even remove any existing content -- is eminently reasonable.

Blogspot blogs, on the other hand, are primarily about the author's content. Destroying that content simply because the author is no longer reachable (e.g. if they have died!) is not a reasonable policy.