Gambling, porn and drugs are not shady unless abused, like anything else. There is nothing morally wrong with doing any of them, however they are categorized as "sinful" from a religious perspective which has made its way into law. They are considered illegal or crimes in many places, to which there is no victim.
If you look at it from the wider perspective of society as well as the beliefs of those who occupy positions of power and make the laws, then that is a minority opinion. Whether we like it or not, most people still believe that those things are wrong even if most members on these forums (including me) might not subscribe to that belief. If Bitcoin wants to become mainstream rather than being merely confined to libertarian circles then from a marketing point of view at least, I think it makes sense to de-emphasize those aspects.
It's interesting to see that you mention Just-Dice and Canadian gambling laws. What's funny is that the we have lottery and gaming corporations in Canada run by the government. They are even able to market and encourage lottery and gaming to the mainstream through TV commercials, radio, internet ads, etc.
We have state-sanctioned lottery games here too. Usually the revenue generated from those go to schools and community projects. As I said, gambling is probably the least controversial out of the so-called "sinful" activities that I listed.