People conform to certain stereotypes, sometimes knowingly, sometimes unknowingly. Mind you,, most people believe that they’re “normal”. That’s a stereotype. Of course there are different stereotypes of normals to different people, but every culture has some sort of stereotype of normal that they basically accept.
While I believe we’re all individuals… at the same time, our mannerisms, assumptions about life, how we think, doesn’t just fall magically from the sky either. We’re shaped and work within those shapes, sometimes busting free of them and absorbing other shapes. Ok, that doesn’t help an ISTP at all does it?