I write the software for my own benefit. I then share it for the benefit of others, but sharing it requires a near-zero amount of effort (`git remote add` and `git push`, basically). I sometimes then derive a benefit to myself when others improve or otherwise contribute to my work.
This only holds as long as my userbase consists mostly of competent technical people who are able and hopefully willing to contribute, and not likely to waste my time.
Dealing with support requests and so-called bug reports from non-technical users that found out about my software from a blog post somewhere is simply not a way in which I'm willing to spend my limited free time.
If I knew that my free software was being used by millions of people, I won't deny that it'd give me a bit of an ego boost, but I am not sure it's really worth anything at all, really. It certainly isn't worth the many hours of free customer support (a thankless minimum-wage job even if it were paid) I'd have to provide.
By contrast, having it be used by a handful of like-minded individuals, who might contribute actual code, or simply talk about other interesting technical topics, related or not, provides a ton of value for little to no effort from me.
So I think I will continue mentioning my free software only in mailing lists, and hope that no one ever sees fit to blog or tweet about it :)
I would be curious if some of you that _do_ care about promoting your work would say why you care about it, though. Do you expect the popularity of your free work to have an impact in your professional career? Or is the satisfaction from providing value to so many people worth the huge extra effort to get there? Or is it something else?