Again, to have economic growth you actually have to have growth. Once you get everyone doing the things that yield maximum economic value, you no longer have growth. You'd have to make more people (exponentially, under current economic regime), which costs physical resources.

As an aside, when talking about economic growth we're looking at economic, not social value, and it so happens that saving lives is one of the less valuable things. You can determine it by looking at the paychecks of doctors or ER personnel.