College offers classes and programs that are neccessary in order to obtain the job one wants. For example, someone who wanted to be a teacher would need to go to college to take the classes they need for that career path.
For trade schools, the answer is similar. Trade schools might offer lessons that colleges don't, such as cosmetology and mechanic.
Basically, Americans continued into college or trade schools after graduation so they can get the certifications and degrees needed for their choice of work.
Trade schools give students on-the-job training in a specialty skill. These types of schools allow students to skip the unrelated general education classes and start classes that are specific to the skills they are looking to gain.
The Missouri Compromise kept the amount of slave states and free states balanced in America. However, the Kansas-Nebraska Act reapeled the Missouri Comp. because it allowed the states to decided if they wanted to be slave or free based on popular sovereignty.
