Having talked to a colleague about blogging the other day, I did some research about how blogs are used by academics, and how students can be encouraged to start blogging themselves. I would say the main reason for blogging is that you can get involved in a wider community of researchers/academics/professionals. This will expose you to new opinions, ideas, tips, and people. Your academic life may feel less lonely, as you can find other people who deal with similar topics or issues to yourself.
Have a look at the links below for some more inspiration: