It is ease to use. At first Blogger is very simple but it also could be customizable. If you need you could get access to the html source code.
It is distraction less. Blogger is a very simple blogging tool. I think you will be more productive and focus about the content. You would not waste time about admin stuff on your blog platform or hosting server.
It is free. As many Google service, blogger is also free. Now I would not have to pay for the blog hosting. Blogger provides a pretty fast and reliable website without ad. But I choose to add some with Google AdSense...
I know that some people will say: it is from Google, so you are the product, they can close your site and bla bla bla... I am perfectly aware of that. I am in IT field, but for the reason's before I choose this platform. I know that is could not fit for everyone and may have some limitations even for me but I do not want to build something from scratch ! I will care about the content.