No matter how well built and sturdy a mobile device is, a little protection does not hurt. The Surface Pro 4 Type Cover is a must have if only for the excellent keyboard. The screen protection, however, is definitely a plus.
But for even better protection, consider the STM Dux for Surface Pro 4. It may add a little bulk to the device, but the siliconepadded corners protect the device from bumps and drops, while still giving you full access to all its ports.
There is also a special area where the Surface Pen can be stored, out of the way and still within reach.