@hyc "I don't see any bears around here" doesn't mean "bears do not exist".
I personally know community managers and technical writers who care deeply about their particular open source projects, so at least, I know that some exist somewhere. I also know they would like to do more, or have had to do less, because they need to spend their time on things that bring in money.
I also know that we traditionally don't place much value on these roles, so it wouldn't surprise me to find tech writers out there who would like to contribute more, but then balk at the amount of their own time and energy they're going to have to sink into it, and go do something else.
Also, "tech writers who want to contribute to open source" is a narrow field to select from. If there's money on the table, we've now widened it to "tech writers who want to be paid". I can definitely find more of those.
It sounds like you might actually be in a good position! You say _almost_ never, so you do sometimes get doc contributions? Are they good? Have you asked those people why they don't contribute more? Have you offered to pay them to do more? On the other side, what kind of user requests do you get about your documentation? Is there stuff out-of-date, missing, confusing, etc? Enough to pull together a list of things you'd like to pay someone to do? Because if you've got money and a job description, you're already most of the way to finding someone to do it!