There are conflicting opinions as to what would prompt someone to keep a daily blog.
Personal fame and reputation seems to top the list - but I'm here to tell you that not everyone is in the writing game for personal gain.
Writing to Write
I tell stories. Some of these stories are about personal adventures. Some are about people I know or respect. Some exist entirely within the realm of my imagination.
I write these stories down for little reason beyond getting them out of my head.
November is National Novel Writing Month and, though I've only "completed" on 50,000-word novel during the event, I still participate every year. Writing is relaxing for me. Few people will ever see those words, and that's perfectly fine.
There are times I write just for the sake of writing.
Building a Larger Platform
Once upon a time, I maintained a collaborative blog with two other writers - we focused on business analysis and projections.
It was a fascinating project. One of our writers successfully predicted a handful of major economic events a full 6 months in advance based on current market indicators. He used the body of content published on the site to launch his career.
Another writer used the platform as a launching pad for a career in sustainable (environmentally-conscious) business development.
Neither would have gotten anywhere without the collaboriative platform. Each writer's success helped build the prominence of a platform that, in turn, contributed to the success and audience of all the others.
Why I'm Writing This Site
As I've said once before, I'm not ready to reveal exactly why I'm maintaining this particular site. But it is an objective that reaches beyond any sort of personal fame or popularity.
There are other reasons to write than personal exposure - why do you keep a blog?