I think alot of it has to do with their "potential" rating. I had guys doing that to me, but Ive noticed that the dudes who are below 82ish for potential usually stay even if they are 18. Could be wrong though, but I have had a few great prospects just leave me too. One guy was 17 potential was 89-93 and his rating if I signed him was going to be 67-70.
Ya I was pissed when I lost him