If you hit the button on the mins knob, it actually turns it off. That's what I do. Either that or just leave it alone. Not sure why every captain reaches up and dials field elevation like that is somehow useful.

This is because the 737 and other Boeing planes come off the factory floor with the default setting to announce "minimums" over the loudspeaker when the plane gets to minimums. In a situation where you transition from an instrument approach to a visual approach, you want to turn that feature off so you don't get a distracting loudspeaker callout at 200 feet or wherever.

Of course, we have to "customize" the planes to fly it like a 200, so no V1, 500, minimums, or even altitude callouts here at Southwest because we are the biggest 737 operator in the world and we do it right, by god.