If you have not read them, may I suggest the FAQ and guidelines to you.

There are many, many reasons why people blacklist. If you want, you can read some here, although I would recommend not to do so, as several of those threads turn bad sooner or later.

Your case: Several of your giveaways seem to be of, let's call it, rather low quality. There are several users who a fed up with seeing floods of those games, some might blacklist you for it. Another reason might be that your library is not public on Steam. Although it is not required to set your library to public, it prevents other users to check, if you activated your wins. That might be seen as suspicious behaviour.