For those of you who use back-button focus (i.e. changing the behavior of the shutter button half-press to be just 'metering start' instead of 'AF + metering start', then using the AF-ON button to start AF), why do you prefer BBF?

I say this because I considered BBF for a bit, then realized it would completely confuse my wife, and we share cameras a lot. Instead, I change AF-ON to be AF-STOP, leave my cameras in AI SERVO almost 100% of the time, and just hold in the AF-ON button on the rare occasion I want focus lock and/or manual override. This saves my thumb from an endless workout of holding in the button, and saves me from having to make sure I'm always shooting in a position where my thumb can always hold that button in.