Falling asleep while driving

My partner and I attended a function in Pretoria and we didn't want to drive from Kempton Park to Pretoria having had a few drinks at the function we opted to travel by Uber, on our way back to Kempton Park our driver started dozing off shortly after we got onto R21 , I thought not to panic and softly tapped him on the shoulder to awaken him , he then dozed off aff as we approached Birchley Acres and he went off the tar road onto gravel road. I don't understand why he accepted the ride when he clearly was tired , we were very fortunate to arrive home safely. These drivers don't take their passengers lives seriously