This is an accounting trick, though. It works because people are willing to pay for a massage and not for whatever the person was doing. But to actually grow the economy, you have to continuously retask that person to ever more profitable activities.
You can also create growth by moving money in circles increasingly fast. Question is, how far we can push bullshit jobs before people get fed up with it? I'm not convinced that "forever" is the answer.
It's not an accounting trick. Different ways a person spends their time genuinely provide different levels of value to society.
If a doctor spends his time saving lives or spends his time watching television, the impact on the world's material resources isn't that different, but the amount of value to society is much greater if he is saving lives.
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.
You can also create growth by moving money in circles increasingly fast. Question is, how far we can push bullshit jobs before people get fed up with it? I'm not convinced that "forever" is the answer.