Looser historic framing
Framing tolerances were looser, and a lot of garages from that period were built with a single-car or odd double-car width that doesn't match today's common 9-foot or 16-foot panel sizes. Add in the climate band here, which the region sits firmly in as cold-moderate, and you've got temperature swings that stress out old header seals and weatherstripping channels that were never designed for an insulated door in the first place.