Mobile Phone in Japan

Mobile phones is quite common in Japan, even students in primary school carry the mobile phone. However, I observed that in the train or subway, using your mobile phone for conversation is considered rude. Near the priority seats, the passengers are advised to switch off their phones. During the journey from Osaka to Kanazawa, the Thunderbird Limited Express has one room (near to toilet) specified for passengers to use their mobile phone. So, it seems that Japanese still consider talking to others in the train or subway is not a good behavior.