Why does Ponyboy say that he hates referring to Soda as a "dropout"? (Outsiders by S. E. Hinton)

Hey I know this one! We read this 2 months ago in English. He hates referring to Soda as a dropout because he thinks drops outs are stupid and "hoods". It says this in the book.

In the first chapter of "The Outsiders," Ponyboy and Sodapop are going to sleep and Pony asks Soda, "'How come you dropped out?" I have never gotten over that. I could hardly stand it when he left school." (pg 17)

Ponyboy loves Sodapop more than anyone and Sodapop defends Ponyboy. When Sodapop dropped out of school it left Ponyboy there alone. He missed having Sodapop in school with him, and he felt like Sodapop shouldn't have to work instead of going to school