You don’t have to be but it helps immensely. Makes the selling job to kids more difficult if you are looking at last year or two of your deal. Kids don’t ever sign with the school just the coach.
Now with kids being able to leave and not sit out with the rule changes the contract maybe doesn’t matter so much. Coach gets fired they can leave without penalty.
Makes me wonder though if that now makes admin more conservative firing a coach. The majority of your roster can now just up and leave.