I love 1km1kt.net for what it is, a small community of designers with which I freely trade ideas because no money will be made off the games anyways. A couple of reasons why we don't have players in this community:
We don't handle the big-name games (D&D, Pathfinder, World of Darkness, and yes, Apocalypse World). Since promotion usually costs a lot of money over a long period of time, creators of free games are not likely to engage in such behavior. Yes, I know there are exceptions to the money thing (Apocalypse World), but it took roughly a decade to build its audience.
People assign value to games based on their price. A professionally produced game is more likely to have gone through several phases of testing and editing. Yes, there are exceptions, but if you don't playtest your game before uploading it, you're part of the problem. People don't want to waste time finding out that their free download isn't playable, and are willing to pay for something that is.
Yes, more players would be nice, but that would likely involve making changes to 1km1kt.net (the free, raw, unplaytested RPGs) that I hope will never happen.