A newbie can't set signatures (or only very short ones), so there's no point in letting them join signature campaigns. It also encourages account creation spam, so the minimum is usually Junior Member for these two reasons.
Hello, excuse me for disturbing. I'm a newbie with 28 activity points and I have 31 posts. My activity points don't update since yesterday's evening. All of the posts were not spam, over 70 words, one with 350 words. What do I do? I need to rank up to Jr. Member.