Draft picks are always evaluating their future, some player’s might want to finish college, play professional hockey, continue playing college ball, or skip everything entirely and try to make a name for themselves in pro baseball.
There are different signability statuses that will influence whether or not that player will pursue baseball or go in a different direction. You may get responses outlining their thoughts and the best way to handle it is to meet the demands of the pick and wait it out, continually increasing the offer may or may not increase his decision speed.
You can also change your draft settings to only pick players who are open to signing and playing professional baseball. In the end, some picks just take more time to decide on what they want to do with their future than others. Much like in real life, they need to evaluate what is best for them.