Brands reach for it when the clothes are right but the casting isn't: a campaign that needs more sizes or skin tones, a new market, or a face whose usage period has ended. Reshooting would mean pulling samples back from stock and booking a new day for products that are already live.
The risk is in the garment. Swapping a body changes shoulders, arms and posture, and the clothing has to follow without the print shifting or the hem moving. A good swap is checked fold by fold against the original, not just at a glance.
