I have a book on the list. I'm lucky enough that at this moment I'm at an institution that will cover the download traffic. But my prior school actually withdrew that support at some point, and in any event I will retire someday. I don't think I can ask my wife for us to pay for that. (I won't mention the possibility of a deadly bus encounter.)
In thinking about where the work might live in order that I could hope it is available, say, for the next decade, it is reasonable to look at people who can use the traffic to keep their lights on.
I used to use Sourceforge. They became unacceptable. I switched to Google code. They turned off, as I understand it because people were uploading pdf's (pitated ones, but big tech seems not to want to make a distinction like that). Then I used GitHub and in the run up to getting bought they made some changes that I thought looked ominous. So I am now at GitLab. Can you blame me for wondering if it is too much to hope that a site will freely host me for, say, a decade even if I go away?
By the way, I put a stable version of my latest on GitLab.
E.g., registration on some website, or the book only being accessible by some medium that pushes ads.