There aren't really that many of them though, and the Dodgers have just pressed a particular triple advantage (winning, money and like attracting like both dating back to Nomo and with the current group), for two particularly great players (and a third on top of that).
Currently 13 Japanese players in MLB.
Dodgers; 3
Padres: 2
Cubs: 2
Angels: 1
Yankees: 1
Mets: 1
Red Sox: 1
Orioles: 1
Nationals: 1
One of the Padres players, Yu, started his career in Texas and signed his next big deal with the Cubs (rejecting the Dodgers who acquired him in between). The Yankees player, Maeda, is a former Dodger but played for two AL Central teams in between. Kikuchi, now on the Angels, started with the Mariners and played for Toronto and Houston in between.
There's no reason the Phillies couldn't be on that list above. But even Seattle and SF haven't been able to land anyone (has SF ever?). When you look over the inactive players, the two New York teams and the Sox were always just as in the mix as LA and Anaheim and Seattle. It's all still about the about financial imbalance, and there's still an argument that players would do well to not be on a team with so many other Japanese players, for marketing deals.