Earlier quoted context omitted.
That's vulnerable to a different sort of hijacking -- SEO spammers recreating blogs with URLs of deleted sites that previously had a lot of incoming links. It'd also risk destroying historically important content that was published in "one-off" Blogspot sites.
Reddit doesn't let you adopt a subreddit if the mod is active anywhere on Reddit, even if you as a user can't see it. The subreddit has to be completely abandoned and the mod account has to be dead. I see no reason why Google can't have similar policies that if the Gmail that controls the blog is completely inactive to the point where it gets deleted, any blogs it controlled can now be recycled.
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.