Universities offer different kinds of classes. You can be offered to study many different courses or on the other hand to specialize in one subject. I think the second option is the best as you concentrate on the field you are interested in, which is the important thing in studies.
At first sight, having to attend to different classes with different subjects looks to be a good idea. You never know too much and getting further knowledge cannot arm. Also, being able to study in different fields is more entertaining than focus on one subject. For example, if you take a mathematic course, even if you are very interested in the subject, it is relaxing to have once a week the occasion to take you mind off it, and learn about history or psychology.
On the other hand, people attending university classes already have a degree, for instance the A-Levels in England or a Baccalaureate in France. Up to this diploma, you usually have been required to study various subjects. Schools will not focus on one topic, but will provide a vast range of courses such as mathematics, literature or history. I believe that it is a good thing to get students to learn a bit about everything, as it is part of their education and general knowledge, but there comes a stage when teenagers have made up their minds about what they are interested in.
University is not compulsory and from the moment you decide to pursue your studies, you have chosen to specialize in one subject. You already have a lot to learn without being compelled to study other subjects that do not interest you more than that. For instance, I am on a civil engineering course and have been required to take statistics last year. This course has indeed nothing to do with my