Tuco is right. Elite dudes are often put on a "three year" plan; I read this when we were hot on Lewis. Basically, college coaches straight up say, "Hey, come here and kick ass for three years, then declare for the draft, no harm no foul." With this kind of talent, that's just how it works. To add to what Tuco is saying, I think SOMETIMES elite dudes stick around for a fourth year if: A.) that specific year's draft is rich in their position, so they come back for a fourth year to improve their draft stock next cycle, or B.) they just happen to personally value a degree. Both are exceptions, not the rule.