Perhaps a young developer might have other goals in life in addition to building great software? Dropping out of college could certainly give you a huge head start in your career, but the costs are huge as well: missing out on spending four years of your life having fun being around people your age.
The magnitude of how much four years in a college environment can change a person is difficult to underestimate. Some may decide that the experience isn't for them and that they should drop out to start their careers, but it's a decision that must be made very, very carefully.