Why are Haworthia truncata's leaves so flat, anyway?

In this plant profile, I explore the environmental advantages conferred to Haworthia truncata -- a succulent plant from South Africa -- due to its distinctively flat leaves. Haworthia truncata is a relatively common succulent in collections, prized for the distichous, truncate leaf structure. I also explore the best methods for cultivating this stunning plant, including its possible use as a houseplant.
Photo credits:
Haworthia truncata Schönland
observed in South Africa
by Joey Santore (licensed under creativecommons...)
Haworthia truncata var. truncata
observed in South Africa
by Tony Rebelo (licensed under creativecommons...)