This isn't a citywide oddity - it's the math of when the neighborhood was built. Mount Prospect sits about 3 miles from our Arlington Heights base, close enough that we see the same construction wave repeat block after block: houses going up through the 1960s and 70s, which lines up with the broader 1938-2009 range across the areas we cover. The service area overall carries a median household income of $109,454, and Mount Prospect's own figure sits close behind at $103,911 - high enough that owners here usually choose insulated steel over the bare single-layer doors that came standard when these houses were framed, but that upgrade is exactly what triggers the header and wiring checks above.
Climate plays a role too. This region sits in a cold-severe band, and a door built for 1969-era garages wasn't designed with today's insulation expectations in mind - another reason installs here run long on the inspection side.