If marijuana has more carcinogens than cigarettes (as most doctors say) than why is it not definitively linked to cancer like tobacco is?

Says who? We know less than we wish we did about cannabis, and we're simply not seeing cancer wards full of stoners despite the drug having been part of life in the US for decades. Much of the scare stuff we've been told during these decades is politics. Forgive me -- anybody who claims that "most doctors say" the stuff has "more carcinogens than tobacco" is simply lying to you for their own reasons.
How did you conclude. How did you conclude that? Have you done an extensive literature study? And if such a study (most likely would have been retrospective in nature) has not been done it does not mean that smoking marijuana is not harmful. Your line of reasoning is very similar to arguments I hear from others that use marijuana about how "it is not harmful " in other ways also.