Religion and drug use are incompatible in their natures. Take marijuana... some people use it for shits and giggles, but real users take it to expand their mind. Same is true with other drugs. That's a problem as far as religion goes because by most measures, the mind expansion brought on by drugs (opium in particular) is very similar to a high stage of the religious experience, where you're so intune with yourself that you perceive yourself to be one with god/universe.
According to religious doctrines, getting high and "seeing Jesus" (or equivalent) is cheating. Even Confucius chided a disciple who achieved mind expansion when "a patch of grass flew into his fire and he inhaled the smoke." A man has to be disciplined, virtuous, have a clean heart, etc., in order to achieve the higher levels of understanding. For religions to accept drugs is to say that chewing a psychosyblin mushroom cap is just as an acceptable way of coming closer to god as a lifetime of religious study.
You probably know that I am a proponent of legalization of drugs (most drugs,anyway. Anything that makes you throw up like heroin, PCP and DMX should be illegal.) I also like the meditative part of religions (which is why Judaism appeals to me - tons of meditation and study, very little crowd control) and I have to say that the "proper" use of drugs is incompatible with the "proper" practicing of religion.
My solution, of course, is to have drugs be legal - but I don't think it makes sense to wait for religious institutions to give their OK for it.
There may indeed, be a bias in Western religions against "non-alcoholic" drugs (and in Islam, alcohol as well.) Many religions accept and utilize drugs: the the Rastamani use ganja to reach Jah, and the chamans of the Andes chewed on cocoa leaves.
But I think that the (Western) religious stance against drugs is more than a cultural bias. Judaism is the religion I am familiar with the most, so I will use it to demonstrate my point.
Most Jewish "occasions" call for alcohol. However, there's a general limit of 4 cups of alcohol a night (meaning cups of wine or shots of harder stuff) so that there is sufficient drink to open your mind and increase the social vibe but not to take you under its control altogether. (There a few occasions where the 4-cup limit is not in effect.) This suggests that there are percautions against improper intoxication rather than substance favoritism outright.
I have spoken to a few Chasidic Jews (the guys in the coats and big hats) and asked them their opinion of marijuana, and the general answer is "we don't need it." Indeed, I think that they get higher during their meditations than a regular person will with a few bowls, so for them to "OK" marijuana use would be unconscionable - they'd prefer for people get high on themselves. But that was their religious view. Politically, they didn't care if marijuana was legal or not (they certainly didn't think it was evil.)
This is why I brought up Confucius before - regardles of what he thought about drugs, he didn't want his disciples to "cheat" their way to enlightenment. I think it's much the same way in the Jewish community: they don't think drugs are evil, they just don't want them as part of the religion, since the Torah commands the Jews to meditate on the written word of God - but doesn't say anything about preventing non-Jews from meditating on bong hits.
The Jewish texts describe meditation and prophecy (the highest meditative level) in some detail. A man must shed his worldly cares and dedicate himself to God (which is the same as dedicating yourself to self-exploration.) Only then will the person be able to reach the relaxation required for admission to prophecy. I contrast that to my suitmate who took shrooms one weeked and came out of it with a new understanding of the universe. In both instances (religious experience vs. drugs) there's some new understanding of the outside world due to deep investigation of the world deep within. But whereas the religious insight requires mental clarity, strength of character, and commitment, the drug insight requires $40 and a liver. If I were running a religion, I'd want to discourage the latter practice because I'd question the "findings" of a tainted soul (ie, have meditation be a goal to strive for - and perfect yourself in the pursuit of, rather than something cheaply available.)
And of course, you have to remember that in the West, drug use has at various points been perfectly acceptable. There was "nothing wrong" with marijuana until the 1930's, and opium was well received in Europe for decades. It's hard to argue that the religious attitude toward drugs is the result of cultural bias when the religions predate the anti-drug biases by centuries.