Why are Japanese immigration officers so unfriendly!?

Every single time I fly back into Japan, I have the same thought when I go through passport control: "would it kill them to smile?" I have flown into Japan from abroad around 30 times. In my memory, not once, not even when I am traveling with the kids, have I ever got any sort of welcome from the immigration officer. 

I also have been through immigration in dozens of countries around the world and, in my experience, this is the exception not the rule. Even in Russia I got a grunt! Although, randomly I find Dutch immigration officers quite intimidating, but once you talk to them, they warm up! In my experience, Japanese immigration officers don't interact at all. They just put their hand out to take your passport and point to the machine where you get your photo and finger prints taken. No hello, no smile, no eye contact.

I can understand why Japan has a very strict ban on taking photos in the immigration area, but I can't understand why immigration officers are so cold in Japan. Are they trained to be like this? And if so, do you know why? Have you ever met a friendly immigration officer at passport control?