It's up to the channel developers to publish "internationally." Roku doesn't have control over that and each channel has it's own reasons for not doing so, whether public or private.
Also as far as I'm aware, there are no "adult" channels in the channel store (if you find one, let me know via PM and I will look into it). All adult channels are private channels which require a special vanity code to input in order to gain access to them.
As we continue to develop the Roku platform, more and more channels will be added to our international customers as well. Remember: when Roku first came into the market, it only played Netflix. There were no other channels. Although I don't know exactly how long it took to add others, I know it didn't happen overnight. Because the Roku is already established, our international customers will see a far quicker line-up than the US ever had. It's just a matter of patience while we negotiate with our partners and contact our 3rd party content providers.
TLDR; it'll come. Just be patient
C. Shawn Smith