A tricorn is mostly edge, curve, and attitude.
That makes it tempting to overbuild the whole thing. Too stiff and it turns into set dressing. Too soft and the brim loses the line before the day is over.
Leather gives the hat a useful kind of memory. It can take a shape, show handling, and age into the rest of the kit instead of staying shiny and separate.
The early work is all about balance: crown height, brim width, turn-up points, and how much finish the leather needs before it starts looking too clean.