What is the purpose of blogging?

People blog for different reasons: to generally express individual feelings and ideas; to get voices out their head. They can share their skills with the public, possibly even making extra income. People also blog to cure boredom, however at the same time, they are testing and improving writing skills and getting feedback. You can also therefore make new friends this way.
Personally I do not blog - but as you're aware now, there are many reasons to go ahead with doing so!