It's basically Japan's enormous second-hand market for just about everything that's holding back digital sales there. You go into Traders, Bookoff, Gamers, heck even the big electronic stores like Sofmap and Bic and they have entire floors dedicated to second hand stuff - CDs, DVDs, models, manga, books, collectibles and, of course, games.
The West may be more ready for a digital-only future but Japanese market will ensure it won't be all digital for the near future, not while that market is still relevant.
