Most predators do their hunting in the cool of early morning or late evening, resting through the heat of the day, which means the first hour after sunrise is often the most productive time to be out looking.
Beyond the wildlife, the light itself is part of the appeal. Low, golden sun across open grassland makes for the kind of photographs that are hard to get any other time of day, and the air is noticeably cooler and stiller.
Leaving camp before full daylight does mean an early wake-up call, usually with tea or coffee brought to your tent, but most guests find the trade worthwhile once they're out on the plains watching the sky change color.
If getting up before dawn isn't for you, it's worth discussing with your guide, some sightings, like a pride finishing a night's hunt, are only really possible in that early window, so it's fair to know what you might be trading for extra sleep.