I journal things so that I can stop thinking about old ideas, and polish up the good ones for publication so that people the PageRank gods direct my way can share their related new ideas. My audience is really Google, rather than any community of subscribers. Reviewing the average time since last post metrics in the Coders folder of my RSS reader, it seems I'm not alone. A lot of people blog perhaps once a year, which is why the aggregation is useful.
I often blog as a form of longer lived documentation for ideas shared on social media. I'll take some of the more inspired posts I've written up on StackExchange or Reddit and repost on my own blog. As I write this I realize I could polish up a few book reviews. In large part my goal is to reduce my role as a digital peasant, generating content for someone else to monetize.
I also blog as a low effort low cost homelab. Learn how to write CSS, learn how to use Jinja templates, learn how to write Chef and Terraform. Learn how work within constraints, to optimize results without straying beyond the free tiers. Learn how AdSense works, how referral systems work. The blog provides a platform for motivated experimentation, so even though I have yet to get my AdSense check, it's proved valuable as a professional experience.
It's also an exercise in hubris. I found out last week that my blog had been offline, and that system that I had set in place for monitoring that was also offline. Pingdom cancelled their free service and it seems I ignored their warning emails. And it seems that Chef, which is responsible for keeping services up, itself stopped working, presumably due to memory pressures from working within the free tier. A self inflicted wound really, since I know this happens and chose to live with the consequences.