I will give you a couple of reasons why. If you are at a D1 school like Kansas, Kentucky, Duke, or UCONN you should have a pretty good chance of getting a good education. Another thing is that you improve with four years of practice and play for example Tim Duncan, Doug McDermott they had four years of experience and they are two amazing ballers. Heck McDermott won the Naismith award. Your team over time rebuilds and then you have a better chance of winning the national title with a more strong team.
Yes, college basketball players should be required to go to school for four years, because they are there to get an education, not to play basketball. The vast majority of college basketball players will not play in college. If they are focused too much on basketball, they are not getting an education. They should be trying to learn, not play a game.
College basketball who receive scholarships should be required to graduate or pay back their scholarships. Colleges utilize a lot of scholarship dollars to attract top athletes. Unfortunately, for those athletes, academics take a backseat to sports. This is not fair to those attending the institution for its academic merits and who were passed over for scholarships in favor of athletes. College basketball players should, therefore, be required to pay back any athletic scholarship they receive if they do not graduate.
I think they should stay at least 2 years in college. It would help in the development of the players as both players and as young kids becoming men. A lot of these guys are leaving because of miss information about their Draft position and how a certain team feels about them. 2 years to focus on school and becoming a better player would do good for them and the success the have at the next level.
They should not be told how long they have to stay in college, it is their choice. If they leave they have a job ahead them where they can earn millions and they get to make the choice for what is best for their nba career, but if players decide to stay four years and develop their game that is fine. Even when they are in the nba they can still go back to college during the offseason to finish their degree, for example that is what Stephen Curry did, so if their nba careers fail they can still get their education. Just because they left college early doesn't mean they are not going to finish their education