2. Sexton has never won over Will Hardy
Despite Sexton proving his scoring abilities even before the Jazz acquired him, he's never quite earned Hardy's trust. This is best evidenced by the fact that Sexton still isn't seeing the consistent minutes in Utah that he did in Cleveland.
Sexton's minute load once topped at 35.3 minutes a game with the Cavaliers, but in what may have been his most efficient season ever, Sexton averaged 26.6 minutes a game. Not only that, but in 126 games in Utah, Sexton has started in 66 of them. Barely over half the games he has played in.
Now, as for why Hardy doesn't seem to trust him much, that is anyone's guess. Sexton's production not turning into team success will make it difficult for him to shed the "Good stats, bad team" label until further notice. Perhaps he believes this is as good as it gets from Sexton in terms of how well he plays, and in turn, how the Jazz play with him.
Sexton may very well thrive with the right coach for him. That just doesn't appear to be Hardy.