Imagine that you head out on a trip not knowing where you are going, then after driving for a few days you decide that you want to end up in New York. You might find that you're no closer to N.Y. than you were when you headed out in the first place. If saving time and money is important to you, you will want to decide where you're going as soon as possible. However, it is also true that you can often start a trip with just a general notion of where you want to go. Using the New York example, if you knew at the beginning that you wanted to be somewhere on the East Coast, you could drive for many days and miles before having to decide exactly where on the East Coast you wanted to go.
College is much the same way.
Many students do not know which program they will pursue when they begin taking classes, but they can often start with some general courses while they are making that decision. However, it is also true that the longer students wait to decide, the longer it is likely to take them to finish their college education. The map below provides a graphic illustration of this point. If you begin driving from Redding to the East Coast and decide after 4 hours that you are going to go to New York, you will arrive sooner than someone who decides to go to New York after driving for 4 days. You have time to plan a direct route from Reno, but it's too late to plan a direct route if you are already in Memphis, Tennessee.