As others have mentioned KLM, amongst others, have tried doing the Southbound to Capetown during daylight.
It has to leave AMS by 0900 to arrive in CPT at 2300 because of the time change. It makes it very difficult for connections at either end, and although CPT is safer than JNB, who would want to arrive in a strange city at midnight with all your worldly belongings with you. There are similar problems on the Aussie routes with aircraft sitting on the ground at both ends during the day.