I don't think people categorize, Socionics does. People seek explanations.
People ask, "Why does he do this, why does she do that, what does that behavior/action mean?", etc.
The Socionics "explanation" is, "It's because of Fi" or "That's Fi-related behavior". But what they're really saying is, "That behavior fits in with Fi classification". They expect an explanation, and what they get instead is a classification.
Am I saying that classification is wrong? No, what I'm saying is that people are seeking explanations, and not just classifications.