Daylight is the light people already know you in. Casting directors, clients and audiences have seen faces in it their whole lives, so it reads as true in a way a beauty dish never quite does. The moment a portrait looks lit, part of the viewer starts assessing the photograph instead of the person.
The practical benefit is bigger though: nobody is nervous in daylight. There is no bang, no recycle time, no waiting while I chimp at a histogram. We just talk, and I shoot while you are talking. That is where the frame usually is.