Revenue may play a part, but perhaps not nearly as much as you suspect. I think that perhaps a reluctance to act for fear of compromising someone's right to free expression plays a bigger role.
When it comes to revenue - I suggest taking a look at the two alternative health sites that others have compared CZ too whilst lamenting CZ not having higher rankings and traffic. Mercola's site is filed with ads, albeit for his own products. And take a look at Natural News. Besides the Google Ads being much more prominently displayed, look at all the sponsors ads on each page now. Trust me, those cost an arm and a leg - the sponsor ads here at CZ are but a fraction. And that does not include the ads in the daily NN newsletter, which also cost some serious coins.
If revenue were the driving force here, then I suggest that CZ would look much more like NN or perhaps Mercola. Personally it wouldn't really bother me to see more aggressive and prominent advertising on CZ. The fact that we don't see it suggests to me that revenue is not as important as some perceive it to be.