I think they have a place in the darker areas of a machine, where there are lights, but not quite enough.
Another place is in the roll over lanes at the top. On some machines it's really crowded/bright there, and a brighter bulb makes it easier to see for the skill shot and to show non-players what to do (with the flippers) easier.
I really don't like them everywhere as they are too bright for me to enjoy a game...I guess I've gotten used to #47 bulbs.
Robert