Why we plane these massive slabs

Lately, I've been getting a few questions about some of the "why's" of my process.  Why do we plane the slabs after they've been kiln dried.  When we are flitch cutting the lumber, why do we cut them so thick.  Above is a pic of a 16' long slab we are in the process of planing today.  With the Lucas sawmill, we cut it into this piece of organic edge lumber several years ago.  During the drying process, the oak slab went through a tremendous amount of stresses, as the moisture was removed, and the slab moved and shrank.  Each slab, tree, species reacts differently.  This pic shows a 1 inch buckle down the middle of the three inch thick slab.  We will plane it down flat, on both sides today and probably end up with somewhere between a 1.25" and 2" thick.  

Robin Wade