Attempt? Relativity? You are interested in MBTI and stuff, but you take psychology and astrology to the same level...
Ok, I'll give you my thought. Psychology is a science, it is really an "attempt to enable us to understand other people better" (I would change it to - understand ourselves better - attempt to understand the others without understanding yourself is a complex of superiority).
But astrology... in some ways it's a lot better.
For example, I met Senorita and found out she's a Cancer (just assuming, I don't know your real sign). Well, I want to find out more about that lady - I can go into psychology, try to find more information, improve my knowledge, try to become smarter in other words - but that's all too hard and time-consuming, isn't it?
I'd better open an astrology book and see: uh... oh... Cancer... slowly makes decisions, too much self-concerned, etc, etc, etc. That's it! Bye-bye, senorita, I already know all about you, I don't even have to talk to you! (and you won't prove me anything - I believe in astrology) I found the way how to avoid thinking and stay dumb, how to avoid that hard effort to become at least a little bit smarter.
One of the greatest, Frederick Perls wrote that horoscope is arrogance of humanity. People in feeling of their greatness came so far that they think that even stars and planets care about their miserable life full of lies, deception and other crap.
Well, Senorita, I'm just tired of hearing that I have a "duplicate" nature because I'm Gemini.