Every old building meets one of two ends, and building demolition salvage lives or dies on which one it gets. A building can be stripped, worked over slowly by hand so the usable parts come out whole, or it can be razed, brought down fast with machines that turn everything to rubble. Most of what reaches a salvage shop came out of the first kind of job.
Why survival is uneven
The choice rarely turns on sentiment. It turns on time and money. Stripping is slow, careful, labor-heavy work, and labor costs. Razing is fast and cheap. A developer on a schedule razes, because there's no line in the budget for saving a mantel. Salvage happens in the gaps: when a teardown runs slow enough, when someone sees enough value in the parts to justify the hours, or when a salvager buys the right to strip before the machines show up.
Survival comes out uneven as a result, and often unfair to the pieces. A fine fixture in a building razed on a tight schedule is gone, no better off than the plainest thing beside it. A plain fixture in a building stripped at leisure comes through fine. What a piece is worth matters far less than which kind of job it happened to be in.
The push toward deconstruction, taking buildings apart on purpose to recover what's in them, starts with that first call. It says the brick, doors, mantels, fixtures, and hardware justify the extra hours, and that razing everything fast wastes material we can't keep affording. Whether it wins comes down, again, to money: whether saving the material pays.
So read a surviving piece as partly luck. It was in a building that got the slow end instead of the fast one. Plenty of equally good pieces were in the other kind, and nothing came out of those.