“I have anxiously awaited the arrival of those such as yourselves. My names Megumin! My calling is that of an arch wizard, one who controls explosion magic, the strongest of all offensive magic! Do you, too, desire my forbidden strength, which is so almighty, I’ve been ostracized by the entire world?” – Megumin
My calling is that of an arch wizard (in bold above)
My name is that of Michael. No god am I, but one who serves.
A Barons title is that of a lord, but he may opt to be referred to as Baron (or Baroness) versus lord.
My job title is that of Head of Commercial Operations, however most of the team call me the Director.
In all of these sentences, why they use that of instead of just saying "A is B", such as "my calling is arch wizard"?