An excellent question. I am no expert, but my understanding from years of observation is that thanks to various legal commitments there is little interest in having someone under contract before camp begins. No one wants to pay a signing bonus until one has to, after all. The first pick is always different, but in general, the situation leads to last-minute decisions, which means that the smallest disagreement can lead to a hold out. That is annoying for fans, but it has been the pattern for at least the last decade, so I would not expect it to change.