[jacobrobbins]

wood expansion is a big factor for wide flat pieces. Non directional wood products like MDF are used in cabinetry because they do not expand to anywhere near the same degree as solid wood. If you want to use solid wood you have to float it in panels, like you sometimes see on doors. But that adds a lot of complexity. For cabinets where you have dozens of moving pieces using MDF (or plywood) is much better for the reliability of the moving parts.