Why do dry cleaners use wire hangers for clothes?

Dry cleaners in London (and, to a lesser extent, uniform rental agencies) use wire hangers as a way of clothing storage and transportation that is so cost-effective that it is included in their services.

The shape of hangers is meant to match the shape of our shoulders. When they're not on our bodies, they can help clothes keep their natural, just-off-the-model appearance. The ideal hanger should match the body's shape, with a broad base and moderate slopes on either side.