Why do you need single shot? Hit BBF in ai servo and then take your finger off. That is single shot focus. My * is set up to change focus points for BIF.
I prefer the beep to know I am in focus. Also every situation does not require Al Servo so it is nice to always have it handy with a press of a button encase some action happens in front of me. The point of my setup is you will always be prepared. Al Servo doesn't always work great with stationary subjects.