Moreover, you can earn money by just sharing your knowledge. Had there not been blogs, you wouldn't have gained so much knowledge from the Internet. They have become the main source of information and millions of users use Internet to find something.
There are numerous reasons to start a blog or website:
Firstly, by starting a website you are literally becoming part of the online blogging community. You can connect with them, share your interests, get feedback from fellow bloggers, put across your opinions and much more. This way you improve your understanding on a particular subject by contributing and coordinating inside a team to build an effective website. It also helps you promote your work and let the world know that you exist.
Having a blog requires you to keep yourself updated with the current trends, which means you are ultimately gaining knowledge. It improves your understanding on a specific subject that you are interested in. For instance, if you start a website on photography - by the time you publish 10 articles, you would have gained enough knowledge on that topic. With curiosity, you learn new things and give it back to the world in the form of a website.
But why should anyone research or learn before writing any article? Because, you cannot write without knowing something and you cannot know without reading something. You see they are inter-related.
The most important reason people blog is to make money. Now that you are reading this, I'm sure you have the same thought in your mind too, right? Monetizing a site isn't that difficult if you intend to honestly share useful and relevant information, neither is it a cake walk to build an effective website. You should understand the various blogging concepts and the basic elements that run them.
To have a successful website you need traffic, to gain traffic you need to optimize it for search engines (that's where you get relevant traffic and the whole process is called as Search Engine Optimization), to retain that traffic you need more content and for more content you need more articles. Once you have enough visitors, its time to monetize, by displaying ads. There are numerous advertisers searching for authority blogs with quality content to promote their products. Here's a list of popular advertising networks.
I have discussed only the most important points why you should be blogging leaving the rest to your imagination.