Maintaining your own blog is hard work. It's bad enough trying to come up with, and write about, interesting topics on a regular basis. But to add insult to injury, you don't even get paid!
However, I think blogging is essential, for reasons I'll describe. And as for the payment aspect, I regard the time spent gratis as part of my marketing budget.
Here's how blogging helps.
Regular updates keeps you in the public eye
... or at least that part of the public that is interested in you. Obviously you have to help this process by engaging in social media and taking account of search engine optimisation in your blog titles -- see The basic rule of blog headlines.
Posting blog articles encourages people to look at your website or blog
Stated like that it all sounds rather obvious, but what I've found is that if I post an article today, there is a spike in my blog traffic -- but not necessarily for that particular article. It's as if posting the article reminds people that my blog exists.
A blog establishes you as an expert
This especially applies if you are a non-fiction writer, but I think it also applies if you write fiction too. For example, you can post "behind the scenes" articles describing how the health service works (if your stories are set in a hospital).
A blog acts as a showcase for your writing
Publishing your own articles on your own blog doesn't have as much cachet as having your articles published by someone else, but it's better than nothing. A would-be commissioner of your work can at least see whether they like your writing style and so on.
A blog audience can be informed about your activities
If you're doing a book signing, running a competition or are about to have a new book published, your own blog is the ideal place to tell people about it.