Why?

Do you understand what you are asking? Cabinet boxes -- the bottom, sides and top are typically made from sheet material like plywood.

If you really want all solid wood, find a local woodworker. Someone building custom furniture and probably not someone building normal kitchen cabinets.

Yes, I understand. I’m specifically trying to avoid MDF, particleboard, laminates, and other highly engineered materials. I’m open to high-quality plywood for the cabinet boxes if that’s the better structural choice, but I’d like solid wood for the doors, drawer fronts, and face frames. I’m trying to find the most natural, high-quality option possible.