Gomer is right about tradition and airplanes - the jacks are typically down under the instrument panel. Helicopters *generally* have their plugs closer to the pilot's head, up high, like in the overhead panels. Straight cords would get tangled in the collective.
Even into the 1970's there were really only two helicopter headsets: David Clark and Telex. Both had straight cords. Eventually David Clark wised up and came out with the coiled cord.
Headsets and coiled cords for helicopter pilots - it was like putting peanut butter and chocolate together. The rest is history.