My dad is currently on Marinol to counter chemo side effects, and I wish he could take the real thing. First it would be a hell of a lot cheaper. Secondly, from what I have read, there are some differences between how Marinol gets digested and broken down into usable components, versus the much easier pathway via the lungs of inhaled THC. Particularly if he was using a vaporizer and not smoking it.
It's not an option for him so glad to have the FDA approved and expensive as hell Marinol. But it's not as simple of an issue as your rant suggests.