Success breeds success. Word is out that if you are good enough to be allowed to walk on at Oregon, you will ultimately break 4:00. Very few milers good enough to make that team that run all 4 or 5 years under Powell don't break 4:00.
Most other schools around the country have never even had one 4:00 guy. At Oregon you get to train with a boatload of them everyday and you become like those around you. You get the mindset like it's no big deal to break 4:00. It's actually expected as a first step toward eventually contributing to the team.
Everywhere else (practically), breaking 4:00 is a lifetime, stretch, fantasy goal. Almost considered unrealistic.