The point of the activity bar is to discourage spam and encourage constant participation. We used to have people who would come on one day a week, post 100 posts of dubious quality (I'm not exagurating at all), then barely show their face. The activity bar forces them to participate on a more constant basis and hopefully discourages spam. The bar is set low because it's supposed to be a goal that everyone is capable of reaching without spamming. 100% activity means "I am a committed contributer to the community," not "I am the 1337 master, bow to my awesomeness." The post count is still there (unless you disable it), so it's not as if your additional contributions go unnoticed.