Often people just use the term "blog" as a generic term for creating web content... So for example often when I say I just published a blog post, I do not necessarily mean I wrote about how I my day went - I often just mean I put a post onto my site containing some content that I want to rank.

But, one of the reasons why people who do blog blog is because they have a following... So for example if I had a website about running, I could blog about how my progress was going because I'd likely have a following who would be interested in that content - so whilst it might not necessarily benefit search engines, it could benefit the people who followed me.

Hope I haven't just totally confused things there lol, it's actually kinda hard to put into words...

If you're referring to blogging here at WA, that has no impact on the search engine ranking for our sites.