Paavo works at a high school level for two reasons:
1) High school kids really need to believe in what they're doing. If you tell them that doing 100 one-armed pushups like Rocky will make them run fast, they will believe you and will run faster. This psychological aspect is often overlooked.
2) The Paavo system includes all of the aspects of any successful training program: running every day, long runs, tempo runs, and intervals. The Paavo evangelists will tell you that it's THE ONLY WAY, everybody else is wrong, our runners are at an advantage because they do this system, etc. They make it out to be a supplement to the Ten Commandments that Moses brought down from Mount Sinai but kept to himself for a few thousand years.
So why don't college programs and elite runners use it? Because their coaches are able to think for themselves and not rely on a program that a stranger at a coaching clinic wrote for their athletes. They make a long term plan but adjust the plan daily based on fatigue, soreness, performance, etc.
They also know that placing time requirements on every single run and every single interval saps the joy out of running. What difference does it make if you do an easy run today at 6:20 pace or 6:40? On an easy day, if 6:40 is enjoyable and 6:20 is a chore, why not do 6:40 for a change? Such limits turn an enjoyable sport into drudgery.
Most of all, they don't create a culture in which the ultimate badge of honor is how many days in a row you've run. They don't run their athletes into the ground because "Paavo" tells them that they have a tempo run scheduled for that day. They give their athletes the day off if their legs are dead or they show signs of an impending overuse injury. That day off may keep them from being so dead that they can't do tomorrow's workout, or keep them from getting hurt, or (worst of all) from hating running.