Are you sure they think you are, Yume?
I have one theory about 날라리 if you're willing to take me with a pinch of salt.
I think 날라리 comes from 날아이. 날 is a prefix that means "raw", like 날고기(raw meat) or 날 것(raw stuff), and 아이 is "kid". This term means someone behaves like a kid, i.e. they do as they please even though they aren't kids anymore. Like CoreanBigSis has mentioned, they don't care about their life very much, and they are usually very outspoken. Even when they talk to teachers(Think what a 5 years old kid behaves like)
Well, in a sense, some teens have a yearning for it because 날라리 is usually popular in class and their fashion sense is usually good.
The difference between 날라리 and 양아치 is that 날라리 don't cause any harm to others and 양아치 do.