There are a number of reasons not to apply to a large number, including time and money. Schools charge application fees that can range from $30 to $90, that can add up fairly quickly. There are application fee waivers that your counselor can arrange if your family falls under certain income guidelines. Usually a quick survey of data suggests that the average student applies to between 6 and 10 colleges. The key thing you want to do as an applicant is to figure out what you want from a college and then do some research to find a school that fits your needs. Want a co-op program in a major city, find one, want to study philosophy in New Mexico, find a school that offers it, want to stay close to home, we have a school here on Guam that does a fine job.
Too often students approach the task from the wrong direction, they apply everywhere and hope a school likes them, do some research and find a school that you like, than apply there. Want help researching colleges? Your school’s counselor will have a great amount of information, also try: bigfuture.collegeboard.org, cappex.com, or collegedata.com