Why don't some dr. S recommend cannabis? Is it a lack of understanding of the plant? A lack of understanding of the cannabinoid system? Or lack of care

Pot. None of the above. It is concern for patient due to misuse, dependence upon continued use.
They like their job. Like it or not, the material is still illegal under federal law.To practice medicine on most health plans, a current federal DEA registration is required, which you can lose if they decide you are involved with illegal drugs.Most just don't want the hassle, although it would change if the GOV got out of the process.
No good studies. There are few or no good double blind case control studies using cannabis for treatment. This is the standard for treatment recommendations for most doctors.
None of the above. Cannabis saliva is used for treating chronic pain under the name marinol. It is used to also to control the wasting seen in aids and cancer patients.