Because Northern have stuffed the competition up with making 20's the underpinning grade to first grade.
There should be a reserve grade or take the age back up to 23's like it was a few years ago.
The 20's comp is that far behond first grade it's laughable. A lot of these players could potentially end up being first grade players , but not every kid is physically or emotionally ready to be playing first grade at the age of 20.
But if they aren't clubs have to move them on or try and keep them as an overage player.
Then i think the problem is that some of these kids don't want to be playing 20's once they turn 21 or 22. I know this was one of the reasons that every single club voted against dropping the age back to 20's, but yet again Northern paid zero attention to the requests of their member clubs