I climbed Langley in the mid-1970’s from New Army Pass. There were not only no cairns, I don’t recall a use trail, or any other sign of human passage from New Army Pass to the summit. Route-finding was absolutely no problem. And I am not a great route-finder.
I object to cairns for esthetic reasons. While they can be helpful for navigation, I don’t consider that to be a justification for their existence. Route-finding is part of the challenge of cross-country hiking and mountaineering. And now we have GPS.
Also I think it can be unwise to trust them for navigation, because you often don’t know who put them up. Some people simply like to mark their passage and imagine they are helpful, for reasons I don’t comprehend. The worst case of this I know of is on the Skyline Trail in Palm Springs, where twice someone has painted markers on the rocks in recent years, and in places where the trail is perfectly clear.