The specific courses required depend on a school's policies. However, most programs require a large number of credit hours in your declared major. You also will likely need language credits, natural science credits, social science credits and elective credits. You may also need additional credits in a related major. For instance, an acting major may need to take music or drawing courses while a biology major may need coursework in chemistry or physics.
In the real world, nothing is ever solely focused on a single area for long. Vocational school provides students with training that allows them to perform a given task well. College is more about the experience of a well-rounded education. Students should graduate with a broader world perspective and with knowledge in a number of areas that helps to fuel their future careers. For instance, language classes are required because -- no matter what profession you enter -- writing clear and proper English will be an asset.
One of the main goals of college is to make students better thinkers. It is difficult to constantly improve your reasoning skills when you only learn things from one area. The process of learning how to think, reason and solve problems is something learned in every discipline, and a well-rounded education hones this ability. For many years, the root of the learning tree was considered to be philosophy for this reason. Philosophy is essentially the study of how to think and reason, and it provides a strong basis for learning in any other discipline.
Although education is the goal, most colleges understand that students attend college to get a job. A broader education makes you more employable in many situations. For instance, a chemistry student who completed coursework in psychology or finance would be eligible for a variety of positions within a pharmaceutical company. Someone who only has an education in chemistry is suitable for working in the lab -- and not much else.