Why do we have to say hi?

The school I'm working at has very strict rules, and the teachers and students need to follow the rules. Sometimes I feel as if I belonged to a military rather than a school. On the other day, there was a party called "welcome party" but substantially "punishment party."

You could imagine how strictly I'm asked to greet to them. By the way, why do we have to greet to others. While reading a book by Minoru Becchaku (Betsuyaku), I found the reason. This author seems to be getting famous, but I have appreciated his works since long time ago.

Minoru Becchaku (a.k.a. Minoru Betsuyaku) is a playwrighter, but he writes very funny essays too. He has a sense of humor.

Anyway, after I knew why I have to say hi, I am willing to use any greetings to people at work, who I want to stay away from.

According to Becchaku's work, "How to live our daily life":

幼時我々は親たちに「あいさつしなさい」と常に強制されたのであり，「どうして」という我々の疑問はその度に「うるさい」という言葉で封殺されたのである．（中略）
……あいさつというものは，出会ったもの同士がそれぞれに無害であることを確かめるための手続きである，と一般的にはみなされていて，それ自体は間違いではないのだが，その時我々は同じ世界を共有しているのではなく，全く別の世界にそれぞれ分離されている（中略）つまりあいさつの中には，相手がそれ以上自分自身の世界に近接しないよう警告を発し，同時に，相手を相手の世界に封鎖して閉じ込めようとする，呪術的要素が含まれているのだ．
　　　　　　　　　　　　　　　　　　　　　　　　　　　　『日々の暮し方』（白水社Uブックス）

Our parents have forced us to greet since we were very young. Our questions about why we have got to greet have always been rejected.

... Greetings are the procedure meeting people need to conduct to make sure that they are safe each other. This explanation isn't wrong, but at that time we find ourselves in different worlds rather than in same worlds.... In other words, a person will use greetings in order to warn others not to be closer to his/her own world and to confine them to their own worlds at the same time.