There are many, many reasons a child might need an IEP.
"Students can get IEPs or 504s for a variety of reasons, such as commonly associated learning disabilities, like ADHD and dyslexia. Children can also get them for severe medical ailments you think a teacher should be aware of, like severe allergies. I think that when people realize that reasons for having a IEP/504 are so diverse, the stigma that having an IEP makes you 'dumb or different' will be far less common." — Katie Simon, New York