Ever since they allowed first semester freshman to apply to DCP for their second semester, that has not been offered.
They have always allowed first semester freshman to apply for the CP.
The Career Start Program was like "College Program Light". You only had to be a high school graduate to apply and couldn't be enrolled in college (taking time off before starting college or maybe not planning on going to college). Same concept as CP, but less role options and I believe less course options (and they were also mandatory).
Obviously, things didn't quite work out since they discontinued it. If I were to speculate as to why, it would probably be that someone just out of high school may have a difficult time on this type of program.
Think about what a huge change College is from high school. Especially if you went a distance from home and live on campus. Huge change. People go down on the CP and have a difficult time adjusting to being away from home, having to take care of themselves (mom not around to cook your food, do your laundry, or make sure you get out of bed), and working what is essentially a full time job.
Imagine having to handle that right out of high school without any adjustment time like you get when you first start college.
My guess is that more people had a rough time on that program than completed it and Disney eventually just said "screw it. we will stick to the CP and International Programs".