Yeah the part about Asians being more discrete when it comes to their private lives is really true.. I don't think that most Western fans of Asian artistes might get it, but Asians are quite conservative when it comes to some stuff. As an Asian who knows quite a lot about the Western entertainment industry, I can say that both entertainment worlds are extremely different. In Hollywood someone can become famous by posing nude or releasing a sex tape, but in Asia, if you do that even the press will ridicule you, and you can just "disappear" from the entertainment world altogether. In a way I respect the Johnnys for maintaining a good public image (hey, between Japanese idols or singers like Britney Spears and Lady Gaga, who do you think you'll want your five-year-old kid (if you have one) to emulate? =p) No offense to anyone, but as an Asian, that's what I personally think.
That's probably why the agencies don't want them to be seen in public relationships. Not as much for to raise the stupid hopes of stupid fangirls that somehow single, unattached Arashi members would one day fall in love with them, but to maintain a clean image. They don't want someone who's known for sleeping around or fooling around as the idol people would look up to. Asians are still generally quite conservative anyway.
Hmm.. Random poll, but who do you think among Arashi members would be the most likely to have a girlfriend in private? LOL.
I agree with you since I have been following the asian entertainment industry I find it refreshing that they tend to have such clean images of course there is occasionally a scandal but for the most part they come off as squeaky clean. The western entertainment industry is a Hot Mess women stealing husbands, young celebs flashing their woohas to photogs, the new release of someones sex tape every month I wouldnt want for my children to think any of these behaviors were

. When I watch asian TV shows it seems like they perceive westerners as having loose morals and I cant disagree with them.
So I appreciate that the celebs keep their private lives discrete and avoid scandals. I do think they should be able to date though and I would think most of them do.