Unfortunately, in my experience this is true. It's not for lack of motivation or desire, it's because my day job is stressful and tiring. The last thing I want to do when I come home in the evening is to spend my valuable personal time writing a blog about what I did at work. I would rather spend time with my family, or do something like that.
Of course, I could try to schedule time during work hours to write a blog on the company website by talking with my manager about it. Unless this advances any strategic or political agenda, it's unlikely to happen.