The buildings and the hardware
The mix of buildings affects the hardware we see. Older single-family houses and multiunit buildings tend to have heavier, mortise-style locks or vintage rim cylinders that need specific parts and experience to service; warped doors and settled frames mean latches don’t line up and strikes often need to be adjusted. Apartment buildings typically use keyed-alike systems or master key setups, so rekeying a building can be more involved than changing one home lock. Storefronts and small offices use commercial-grade cylinders and exit hardware, which requires different tools and parts than a residential deadbolt.