I can't debate any specific point in this article. It seems well written and researched to me. Here's what doesn't add up to me. If it's actually possible why

I can't debate any specific point in this article. It seems well written and researched to me. Here's what doesn't add up to me. If it's actually possible why hasn't it happened? It seems like there is all the monetary incentive in the world to get it done. It feels to me like the fact that it hasn't happened supports the idea that it isn't economically viable under the current conditions