Two kind of overlapping reasons.
One is that if any of these seniors had shown as much as these 19 year olds when they themselves were 19, they'd have been in the 2019 Draft or what have you. TSJ, Knecht, Edey, these guys weren't at the level of these other players at the same age.
And then when we're talking about guys that are 23 or more, some of their prime development years, the ones where players can really change and add major new components to their game, have already passed.
But there are still college seniors that turn out to be good NBA players, there is still always appeal to those guys when they've shown high-level NBA skillsets in college. But guys with star potential will always take priority.
