Now, you could argue these other uses are not "medical", but I might retort that that is a semantic point? What is the drug's desired effect? In the case of marijuana, there are many, many users who desire and receive an effect which is not related to nausea or pain; It is therapeutic, i.e., mood-enhancing, AKA behavior management. Hence the expressions "mellow out" or "take the edge off."
In other words, the current rationale for using marijuana medically is to alleviate pain and suffering, but I don't think it is a stretch to imagine a doctor prescribing marijuana in the same way they prescribe Xanax. Hell, if the RX company sends them enough free samples, they'd probably give some away.