Katakana are used for far more than loan words, loan words is just the first example you learn when you first start learning Japanese. Among many other stylist

Katakana are used for far more than loan words, loan words is just the first example you learn when you first start learning Japanese. Among many other stylistic uses, katakana are often used for native onomatopoeia and are used to write native words all the time (usually in cases where the kanji is either not well-known or to give a different feeling to the sentence -- ズルい is a good example of this).