So, why exactly did they include a built-in flash on the D800?

The presence or absence of the flash does not make the camera professional or not. The design of the camera merely follows its expected use. Some Hasselblads trigger studio flashes, some D3s get rain on them. As buyers in the marketplace, we choose the product that best suits our needs/wants - sellers adapt to the larger marketplace. I think the D800 will do well, but only time will tell.

Gerald
http://suresoft.ca