It's not just "often" develops an IEP. Every student who is classified as being special education has an IEP, and this includes gifted students, as well as developmentally disabled students.
One big issue right now is how much to mainstream special education students. Some are able to function in a regular classroom in some areas, while some students are not. Some students may only need special education in math, for instance, but can stay in a regular classroom for social studies or science.
Curriculum also needs to be developed based on cultural issues. Some special education students come from homes where a different culture is prevalent, so their curriculum must be designed to consider these differences. It's a fine line to walk.