The thing with the draft is its not a science and never will be, as much as everyone wishes they could master it. You can analyze the numbers all you want, you've got to look at each specific player individually and make a judgement call. And for all the background work being done, the situation they ultimately land in may have just as large of an effect on their ultimate success in the NBA. A lot of this is weighing upsides too. A GM may know the 3 or 4 year college guy is pretty likely to become some kind of rotation player while the one and done kid has a 20% chance of making it but if he does hes at least a starter if not better. I can see plenty of GMs going for the risky guy, as the safe bet isn't a difference maker in the scheme of things.
But to add to the argument, I think a lot of these guys would be wasting time staying any longer in college. What would Anthony Davis have to gain returning to Kentucky? He dominated as a freshman. Continuing to shit on inferior talent isn't going to help him as much as spending the early years of his career developing against better talent. But you get plenty of guys who don't dominate the NCAA but were highly touted prospects and are very talented kids. Conventional wisdom says those guys need more time in college to get the mental part of the game down, to grow into being a dominant player before moving to the next level. They usually leave early anyway and ride the pine somewhere. Some drop and end up on good teams with strong cultures a la Avery Bradley or Lance Stevenson or Eric Bledsoe. A lot of sort of disappear into the abyss though and you look back and wonder what they could have done if they stayed in college 3 years. Also look at guys like Blake Griffin or Harrison Barnes who didn't have great freshman years but stayed just the one extra year in college. They still came out very young and with big potential, but they had some extra polish that likely helped them contribute as rookies despite still being raw.
And yeah, as an 18 year old I absolutely thought I was a legitimate adult and pretty smart and mature. I'm 23 now and looking back at myself then, I was a complete fugging moron and still a child. And lets be honest, a lot of these guys come from poverty, single parent homes, from the hood, didn't take education seriously, probably have a highly inflated sense of self and a lot of hangers-on influencing them with agendas that aren't in their best interest. I think this is a big reason why a lot of these kids that go to NBA wastelands completely flame out while the ones who go to good teams with strong leadership and culture eventually pan out.
It's the equivalent of the "some people are saying" brand of news. 
