<p>It happens, but usually so gradually you don’t even notice it. Think about friends you had as a little kid, kids who you played with every day on the playground. Not every one of those lasted the whole way through school (if any?). It’s pretty much the same in college. Some friends, even ones you were extremely close to, will fall away as you each grow and mature, some will not. It can be hard to predict which is which in advance, so it’s really not worth worrying about it.</p>