Some people who have asked or answered questions have in their tags section saying that they haven't participated in tags, which isn't right. Is there a reason for this? A lot of people with 1 reputation seem to have this issue.
You mean this, taken right now from your meta profile?
That information is cached (up to 24 hours, IIRC), so that explains why you don't see that information for new users. For other users, the score or number of posts may be a bit outdated.