It has to do with living a simple life, a life of virtue and reducing craving.
From DN 2 Samaññaphala Sutta: The Fruits of the Contemplative Life
"Whereas some priests and contemplatives, living off food given in faith, are addicted to high and luxurious furnishings such as these — over-sized couches, couches adorned with carved animals, long-haired coverlets, multi-colored patchwork coverlets, white woolen coverlets, woolen coverlets embroidered with flowers or animal figures, stuffed quilts, coverlets with fringe, silk coverlets embroidered with gems; large woolen carpets; elephant, horse, and chariot rugs, antelope-hide rugs, deer-hide rugs; couches with awnings, couches with red cushions for the head and feet — he abstains from using high and luxurious furnishings such as these. This, too, is part of his virtue.http://www.accesstoinsight.org/tipitaka ... tml#luxury
Even lay people when they undertake the Eight Precepts, commit to:
8. Uccasayana-mahasayana veramani sikkhapadam samadiyami
I undertake the precept to refrain from lying on a high or luxurious sleeping place.