why to publish a book?

I don't want to talk about "how" to publish a book, because I am still finding information about it, but I would like to talk about "why", which is more important.

Personally, I would like to write a book and I have some ideas, but the question about "why" taking so much effort on a book, when you can find millions of books in bookstores. Well, I will give you some hints.

• As the saying goes "Write a book. Plant a tree. Have a son."  Well, we have to start with one of them. What I mean to say, we are just passing by in this planet. So we have to leave something for the rest, for the future generations. Doing a book is one way.
• Through writing a book, we can express what we have inside, the way we see life. It is a great chance to show the world who we are.
• As teachers, it is a "Must" to have a book. We are creative people, and we must share that with others.
• The topic, you choose it. It can be about being a teacher, you subject, ideas, experiences, creative things, tales, a novel. It is your choice, but always give a personal touch, because outside, there are hundreds of books like yours already.
• You are inspiring others, you are inspiring your students. Your students don't want to read? Well, do something, but do it your own. Don't just say "read shakespeare", say "Read My book".

Don't waste your ideas, and be someone who will go beyond borders with your words and thoughts. If you have the chance to write a book, do it.