There have always been the kids who think they deserve more floor time. Some would leave and sit out a year. Combine that with the new transfer rules and it is no shock that more leave. Think about all the players who didn't get much time early and then started later. Maybe they would have left too if there were no transfer penalty.
However, I will say the track record for SU leavers has really not been good. Most don't do much in other places. We have seen maybe a handful over the years. In addition, kids are less likely to accept criticism that in the past. If you are truly good, you play.