Well, I always carry a WPB parka in the western mountains like the Spring Mountains north of Las Vegas (max. elevation 11,990 ft.) and in Sierra Nevada and the Rockies winter or summer. Like my down sweater, a WPB parka is a safety item, IMO.
Usually it was my Cabela's PacLite parka but now it's my eVent parka. PacLite pants go along in winter and in the Rockies a year 'round. They vent in the lower legs.
I guess as a ski patroller I'm very aware of the threat of hypothermia so a WPB parka seems necessary. And I've found that the Kimtah eVent parka easily doubles as a wind jacket.