Well, if you don't really care if anyone else uses your open source, then it doesn't really matter, right?

The reasons you might care are -- to get more contributors, to make the software more sustainable; fame for your yourself or your company (how valuable is this?); etc.

Being clear on what benefit (if any) you will get from the project being more popular will make it easier to guess whether the 'investment' will be worth the 'benefit'.

But how do you do it? I think you've got to not just 'advertise' in general interest places like HN. You've got to find the community of people who will find your code most useful (perhaps people in the same business domain as you are working), and advertise to them, sometimes direct one on one. Conferences and meet-ups are good for this.

I think you've also got to have really good docs, and really good release management practices (semver, no backwards compat bugs, no encouraging using off 'master' instead of a release, good release notes, etc).

And if still nobody is using it, then I guess they don't actually find your software useful!