I used to think the same way but the longer i deal with my 3 docs & my wifes 4 docs im starting to change my mind,i think its more along the lines of them not knowing anything about mj other than what they've learned in school,ya gotta remember most docs are not taught real world effects of mj,only bs hype.
My pain doc couldnt understand what mj would do for me & he is cool as fuk,all he could see was the pain killing effects of what i was allready taking,if were all being as blunt as possible we all know that even the strongest smoke at 30% levels cant compare with a 7.5 mg vicoden for pk effects, so on that note the docs are right, to a degree.
For my wife & me, using mj isnt the ticket for pain but it does help balance the effects of the pk's & extend their working window,which translates with us taking less pk's,there is also a muscle relaxant effect with mj that cannot be replicated with synthetics just yet,we all need to point this out to our docs to help them learn how helpfull it can be without interfering with the prescribed meds.
I think the more common med mj becomes the more educated pain mgmnt docs will become.