With the young guys, it's a question of whether the team wants to give them more of a chance to improve. It's hard to close the book on guys like Butler or Bolmaro when they're 22 and they haven't had much real playing time. If they just aren't NBA-level talents, then that's another thing, but the Jazz tend to give chances to young players that they thought enough of to draft.
With Dok, it's more of a question of whether he fits the archetype that the Jazz want from the center position. He's not a shooter or ball mover, and if you look at the Jazz bringing in guys like Olynyk and even Zeller, it looks like the Jazz may want more versatility from that position. Also, it's pretty clear that he was Dennis Lindsey's idea. Health questions aside, the Jazz could decide that he'll never be more than a backup and he isn't the type of player that Will Hardy wants to give minutes to.