I believe music is one of the gifts of life that everybody can compare and relate to. Everybody has their own taste in music, and sharing your ideas with others can expand their horizon of music as well. Naturally, half of everybody's music choices depend on friends, the radio, and the media.
To share your thoughts and interests with others is to share your knowledge of other artists and generes. You can influence people with your own likes and dislikes and maybe get others into the same things you are into. It's fun finding others who like the same things as you because you can feel like you can relate.
By blogging and explaining your interests, you can get people all over the world to read your words and spread your interests and maybe even ending up making some new friends who like what you write about.