Don't give up yet! The project is only a few weeks old, and I think it is just not well-known enough yet to be used by the whole SFML community. It would be a huge pity if you dropped support, SFMLUploads really has big potential.
Concerning the code snippets, it seems like my initial fear has come true: People don't know why they should post code on your site, if they can directly insert it into forum posts. For the more elaborated codes, users probably use the Wiki.
I think sfmluploads.org's main application lies in the screenshots. I believe there have been more than only 4-5, at least I have sometimes seen pictures from your site in this forum, and I have just uploaded two myself. The other important use case is archives for people who don't have a website to host their projects (mostly small games).
Maybe we should all spread the word and recommend your site every time an external file hoster is used, that's probably the best way to make SFMLUploads more popular.