I suppose this question is as important as why do people read them. Hopefully, there is some commonality of purpose :-). A quick list of reasons:
- To practice writing
- To express themselves creatively
- To voice an opinion
- To respond to other bloggers
- To get attention (good or bad)
- To make a record of what they were doing and saying at a particular time
- To explore a topic in search of deeper understanding of it
- To entertain
- To inform
- To teach
- To be remembered
- To make an impression
- To get a job
- To inspire discussion
- To advocate action
- To persuade
- To woo