Basically most dancers fall into one or more of the following categories: classroom dancer, social dancer, examination dancer or competition dancer.
Classroom dancers are those people who only dance in class and no where else. If you just like the atmosphere of the class, want to get to know people, or get some exercise, it's fine. If not, then it's really putting in time, effort and money to learn something which is not put into use.
Social dancers are those dancers that learn dancing and want to use their new found skills to dance at functions and dance places. This people are really enjoy their dancing and make use of their new skills.
Examination dancers are those that learn dancing for the sake taking dance exams which fall every year. Most of the time they spend up to a year preparing for the exams. While the preparation would help them dance technically correct, dance examination preparation does not prepare you for dancing in a real situation as examination dancing is based on a fixed routine with a fixed partner.
Competition dancers blend the versatility of the social dancers with the technical correctness of the examination dancers and add more flair and finesse to the dance. The stage of preparing for a dance competition really improves your dancing tremendously, regardless of how well you do.