BAU provides forward mobility.
Strategic work provides upward mobility.
When you put this into context against the backdrop of the mountain / sphere that you are climbing, you find that BAU alone will keep you circling the mountain at whatever level that you currently are – at best it will move you forward very slowly.
Combining BAU with Strategic Work however, you will find you start to climb in a forward and upward trajectory.
Strategic work is key to climbing your mountain.