I really don't have an answer. I just need to convince some of the more well known developers to upload their games. I need to try hard sell them on uploading, tell them it costs nothing and will take very little time.

More well known developers are uploading their games over time though, I think more people are starting to discover the utility of the site. Recently got two games from Vlambeer:

http://vlambeer.itch.io/gun-godz http://vlambeer.itch.io/wasteland-kings

So I guess the real answer is time. I need to prove the platform isn't going anywhere and that it has the features that are truly indie friendly.