Tell that to the NBA. "One and one" isn't a creation of the NCAA; it's part of the Collective Bargaining Agreement between the NBA owners and Players' Association. You can call it the "Help keep us from drafting another Kwame Brown" rule.
The central problem with all of this is that there is no viable minor league system in basketball and football like there is in baseball. It would be great if the NBA adopted the same rule as baseball does IRT to the amateur draft, there's a "look" coming out of HS (age 18), but if you go to college, you can't be redrafted until you turn 21 (3 years). If the NBA owners and PA made it part of the CBA, there shouldn't be any legal problems.