For the sake of argument, lets say the NCAA opens its doors to CHL players. I will use the Saginaw Spirit as an example.
Zayne Parekh will be a first round draft pick by some NHL team. Supposed that team would prefer that he play for some major NCAA powerhouse... the reason, playing against older competition. He leaves. The Spirit have lost a valuable asset that they might have traded off for future rebuilding picks. They are now at a total loss, both an active player gone and future considerations for said player lost. He may not go at 18, but what of the following year?