Not everybody approaches education with the same goal. High school and higher education serve different purposes for each student. For some pupils, school is a direct path to a job. For others, it is a chance to learn for the sake of personal growth. Visit any classroom and you'll encounter students with a variety of goals for their education.
Regardless of what you want school to be, most people seem to agree that an education should set you up with at least a basic set of skills. Not a universal set -- no one expects someone who studied nursing to have an identical skill set as someone who studied accounting. But when you have employers posting jobs that say a high school diploma or four-year degree is a requirement, you realize they expect you to have crossed a certain threshold. Still you seem to hear frustrated employers and employees wondering aloud, "Why didn't they teach this in school?"