The buildings and the hardware
The local housing stock affects the locks we see. Many doors are older solid-wood or metal doors with boxy mortise or rim locks; apartment buildings add keyed-alike setups or master-key systems that complicate rekeys and replacements. Storefronts and small commercial entries tend to use heavier deadbolts, exit devices, and rim cylinders, which need different tools and parts than a simple residential knob set. Where doors are older the strike plates are often undersized or the door jamb is worn; that shifts the job from a simple cylinder swap to reinforcing the frame, adjusting the door’s fit, or replacing an entire lockset to match the door’s age and mounting.