MTBI fans also have a lot of this. The websites play into it by pretending some personality combinations are rare, or that any of it is set and doesn't actually change every time you take one of the damn tests, or that you can't force results. So you have the INTJs who definitely think they're better than and smarter than everyone else, or the ENTJs who are categorized as "visionaries" so they're totally going to become a corporate CEO once they're done working on their dad's construction crew. If there are subforums, you'll get to watch people fight over their self-labeled categories.

Also to further your point, there are notable periods of the eastern zodiac where people either try to get pregnant or avoid getting pregnant just because of the good or bad luck attributed to some years. Japan also has an actual word for blood type discrimination (avoiding or not hiring AB or B blood types) called bura-hara.