constant eye contact can make people uncomfortable.  it may lead back to our animal instincts??  but the eyes can tell their own story and it may not be what the person is really saying.  it maybe as you say a shy thing but it can also be a way of showing submission to an other person.  i was told long time ago to look at spot just above the bridge of the nose when talking to people.  but i tend to flow back and forth from the mouth to the eyes as i want to connect to what the person is saying.   thanks for continuing to share life/views from an other country in your blog.  it is always interesting.  

I'm Japanese, so maybe I can explain why Japanese people tend to avoid prolonged-eye contact especially with strangers.

There are some reasons that I can think about. 

1, shy and introverted.  Yes and No.  maybe Japanese are generally shy compare to Westerners, but it can't describe enough why avoids eye-contact.Some Japanese think, it is safe not to insist strongly because individualism and democracy hasn't encouredged and developed so much in its society and in education. It's more like attunument so if surrounding doesn't like to do eye-contact, they won't .(Nowadays, it's changing because of the influence of globalism though)

 and also Japanese tends to be cautious or considerate for stranger. 

2, over-populated, busy and no room to have a little chat with stranger in grosery store or cafe in city area. In some city, picking up on the street is illegal.(I think it is for preventing prostitution) 

3, It's sometimes rude or offensive to stare the eyes whose older person's. I think it is an afterglow of feudal system. People in lower hierarchy couldn't see directly to shogun in Edo era so, avoiding eye-contact was like to show the submission. I personally think that is awkward not to see the professor in classroom and every students are just watching their book with their head down though.

4,  Generally, we Japanese are taught that look to the teacher in the classroom when we were kids and kids usually make an eye contact each other but, for adult, it may be not so common to make an eye-contact.  

However,  it is really depends on the person. Ofcourse, an actor, host and hostes doesn't hesitate to make eye-contact and to make an eye-contact is getting be important in business in Japan.